Herein lies the good part. Many thanks to Todd Eigenschink <eigenstr@CS.Rose-Hulman.Edu> (who thanks Dave Love <D.Love@dl.ac.uk>) for creating `slib.texi'. I have learned much from their example.
Aubrey Jaffer jaffer@ai.mit.edu
SLIB is a portable Scheme library meant to provide compatibility and utility functions for all standard Scheme implementations, and fixes several implementations which are non-conforming. SLIB conforms to Revised^4 Report on the Algorithmic Language Scheme and the IEEE P1178 specification. SLIB supports Unix and similar systems, VMS, and MS-DOS.
For a summary of what each file contains, see the file `README'. For a list of the features that have changed since the last SLIB release, see the file `ANNOUNCE'. For a list of the features that have changed over time, see the file `ChangeLog'.
The maintainer can be reached as `jaffer@ai.mit.edu'.
Check the manifest in `README' to find a configuration file for your Scheme implementation. Initialization files for most IEEE P1178 compliant Scheme Implementations are included with this distribution.
If the Scheme implementation supports getenv, then the value of
the shell environment variable SCHEME_LIBRARY_PATH will be used
for (library-vicinity) if it is defined. Currently, Chez, Elk,
MITScheme, scheme->c, VSCM, and SCM support getenv.
You should check the definitions of software-type,
scheme-implementation-version,
implementation-vicinity,
and library-vicinity in the initialization file. There are
comments in the file for how to configure it.
Once this is done you can modify the startup file for your Scheme
implementation to load this initialization file. SLIB is then
installed.
Multiple implementations of Scheme can all use the same SLIB directory. Simply configure each implementation's initialization file as outlined above.
The SCM implementation does not require any initialization file as SLIB support is already built in to SCM. See the documentation with SCM for installation instructions.
SLIB includes methods to create heap images for the VSCM and Scheme48
implementations. The instructions for creating a VSCM image are in
comments in `vscm.init'. To make a Scheme48 image, cd to
the SLIB directory and type make slib48. This will also create a
shell script with the name slib48 which will invoke the saved
image.
If there is no initialization file for your Scheme implementation, you will have to create one. Your Scheme implementation must be largely compliant with IEEE Std 1178-1990 or Revised^4 Report on the Algorithmic Language Scheme to support SLIB.
`Template.scm' is an example configuration file. The comments
inside will direct you on how to customize it to reflect your system.
Give your new initialization file the implementation's name with
`.init' appended. For instance, if you were porting
foo-scheme then the initialization file might be called
`foo.init'.
Your customized version should then be loaded as part of your scheme
implementation's initialization. It will load `require.scm'
(See section Require) from the library; this will allow the use of
provide, provided?, and require along with the
vicinity functions (vicinity functions are documented in
the section on Require. See section Require). The rest of the library will
then be accessible in a system independent fashion.
Please mail new working configuration files to jaffer@ai.mit.edu
so that they can be included in the SLIB distribution.
All library packages are written in IEEE P1178 Scheme and assume that a
configuration file and `require.scm' package have already been
loaded. Other versions of Scheme can be supported in library packages
as well by using, for example, (provided? 'rev3-report) or
(require 'rev3-report) (See section Require).
`require.scm' defines *catalog*, an association list of
module names and filenames. When a new package is added to the library,
an entry should be added to `require.scm'. Local packages can also
be added to *catalog* and even shadow entries already in the
table.
The module name and `:' should prefix each symbol defined in the
package. Definitions for external use should then be exported by having
(define foo module-name:foo).
Submitted code should not duplicate routines which are already in SLIB
files. Use require to force those features to be supported in
your package. Care should be taken that there are no circularities in
the requires and loads between the library
packages.
Documentation should be provided in Emacs Texinfo format if possible, But documentation must be provided.
Your package will be released sooner with SLIB if you send me a file which tests your code. Please run this test before you send me the code!
Please document your changes. A line or two for `ChangeLog' is
sufficient for simple fixes or extensions. Look at the format of
`ChangeLog' to see what information is desired. Please send me
diff files from the latest SLIB distribution (remember to send
diffs of `slib.texi' and `ChangeLog'). This makes for
less email traffic and makes it easier for me to integrate when more
than one person is changing a file (this happens a lot with
`slib.texi' and `*.init' files).
If someone else wrote a package you want to significantly modify, please try to contact the author, who may be working on a new version. This will insure against wasting effort on obsolete versions.
Please do not reformat the source code with your favorite beautifier, make 10 fixes, and send me the resulting source code. I do not have the time to fish through 10000 diffs to find your 10 real fixes.
This section has instructions for SLIB authors regarding copyrights.
Each package in SLIB must either be in the public domain, or come with a statement of terms permitting users to copy, redistribute and modify it. The comments at the beginning of `require.scm' and `macwork.scm' illustrate copyright and appropriate terms.
If your code or changes amount to less than about 10 lines, you do not need to add your copyright or send a disclaimer.
In order to put code in the public domain you should sign a copyright disclaimer and send it to the SLIB maintainer. Contact jaffer@ai.mit.edu for the address to mail the disclaimer to.
I, name, hereby affirm that I have placed the software package name in the public domain.
I affirm that I am the sole author and sole copyright holder for the software package, that I have the right to place this software package in the public domain, and that I will do nothing to undermine this status in the future.
signature and date
This wording assumes that you are the sole author. If you are not the sole author, the wording needs to be different. If you don't want to be bothered with sending a letter every time you release or modify a module, make your letter say that it also applies to your future revisions of that module.
Make sure no employer has any claim to the copyright on the work you are submitting. If there is any doubt, create a copyright disclaimer and have your employer sign it. Mail the signed disclaimer to the SLIB maintainer. Contact jaffer@ai.mit.edu for the address to mail the disclaimer to. An example disclaimer follows.
If you submit more than about 10 lines of code which you are not placing into the Public Domain (by sending me a disclaimer) you need to:
This disclaimer should be signed by a vice president or general manager of the company. If you can't get at them, anyone else authorized to license out software produced there will do. Here is a sample wording:
employer Corporation hereby disclaims all copyright interest in the program program written by name.
employer Corporation affirms that it has no other intellectual property interest that would undermine this release, and will do nothing to undermine it in the future.
signature and date, name, title, employer Corporation
Things that are labeled as Functions are called for their return values. Things that are labeled as Procedures are called primarily for their side effects.
All examples throughout this text were produced using the scm
Scheme implementation.
At the beginning of each section, there is a line that looks something like
(require 'feature).
This means that, in order to use feature, you must include the
line (require 'feature) somewhere in your code prior to the use
of that feature. require will make sure that the feature is
loaded.
(require 'array)
#t if the obj is an array, and #f if not.
When constructing an array, bound is either an inclusive range of indices expressed as a two element list, or an upper bound expressed as a single integer. So
(make-array 'foo 3 3) == (make-array 'foo '(0 2) '(0 2))
make-shared-array can be used to create shared subarrays of other
arrays. The mapper is a function that translates coordinates in
the new array into coordinates in the old array. A mapper must be
linear, and its range must stay within the bounds of the old array, but
it can be otherwise arbitrary. A simple example:
(define fred (make-array #f 8 8))
(define freds-diagonal
(make-shared-array fred (lambda (i) (list i i)) 8))
(array-set! freds-diagonal 'foo 3)
(array-ref fred 3 3)
=> FOO
(define freds-center
(make-shared-array fred (lambda (i j) (list (+ 3 i) (+ 3 j)))
2 2))
(array-ref freds-center 0 0)
=> FOO
array-shape returns a list of inclusive bounds. So:
(array-shape (make-array 'foo 3 5)) => ((0 2) (0 4))
array-dimensions is similar to array-shape but replaces
elements with a 0 minimum with one greater than the maximum. So:
(array-dimensions (make-array 'foo 3 5)) => (3 5)
#t if its arguments would be acceptable to
array-ref.
(index1, index2) element
in array.
The functions are just fast versions of array-ref and
array-set! that take a fixed number of arguments, and perform no
bounds checking.
If you comment out the bounds checking code, this is about as efficient as you could ask for without help from the compiler.
An exercise left to the reader: implement the rest of APL.
(require 'array-for-each)
(require 'alist)
Alist functions provide utilities for treating a list of key-value pairs as an associative database. These functions take an equality predicate, pred, as an argument. This predicate should be repeatable, symmetric, and transitive.
Alist functions can be used with a secondary index method such as hash tables for improved performance.
assq, assv, or
assoc) corresponding to pred. The returned function
returns a key-value pair whose key is pred-equal to its first
argument or #f if no key in the alist is pred-equal to the
first argument.
#f if
key does not appear in alist.
(define put (alist-associator string-ci=?)) (define alist '()) (set! alist (put alist "Foo" 9))
(define rem (alist-remover string-ci=?)) (set! alist (rem alist "foo"))
(require 'collect)
Routines for managing collections. Collections are aggregate data structures supporting iteration over their elements, similar to the Dylan(TM) language, but with a different interface. They have elements indexed by corresponding keys, although the keys may be implicit (as with lists).
New types of collections may be defined as YASOS objects (See section Yasos). They must support the following operations:
(collection? self) (always returns #t);
(size self) returns the number of elements in the collection;
(print self port) is a specialized print operation
for the collection which prints a suitable representation on the given
port or returns it as a string if port is #t;
(gen-elts self) returns a thunk which on successive
invocations yields elements of self in order or gives an error if
it is invoked more than (size self) times;
(gen-keys self) is like gen-elts, but yields the
collection's keys in order.
They might support specialized for-each-key and
for-each-elt operations.
#t to collection?.
do-elts is used when only side-effects of proc are of
interest and its return value is unspecified. map-elts returns a
collection (actually a vector) of the results of the applications of
proc.
Example:
(map-elts + (list 1 2 3) (vector 1 2 3)) => #(2 4 6)
map-elts and do-elts, but each
iteration is over the collections' keys rather than their
elements.
Example:
(map-keys + (list 1 2 3) (vector 1 2 3)) => #(0 2 4)
do-keys and do-elts but only for a single
collection; they are potentially more efficient.
comlist:reduce-init
(See section Lists as sequences) to collections which will shadow the
list-based version if (require 'collect) follows (require
'common-list-functions) (See section Common List Functions).
Examples:
(reduce + 0 (vector 1 2 3)) => 6 (reduce union '() '((a b c) (b c d) (d a))) => (c b d a).
some (See section Lists as sequences) to collections.
Example:
(any? odd? (list 2 3 4 5)) => #t
every (See section Lists as sequences) to collections.
Example:
(every? collection? '((1 2) #(1 2))) => #t
#t iff there are no elements in collection.
(empty? collection) == (zero? (size collection))
(setter list-ref) doesn't work properly for element 0 of a
list.
Here is a sample collection: simple-table which is also a
table.
(define-predicate TABLE?)
(define-operation (LOOKUP table key failure-object))
(define-operation (ASSOCIATE! table key value)) ;; returns key
(define-operation (REMOVE! table key)) ;; returns value
(define (MAKE-SIMPLE-TABLE)
(let ( (table (list)) )
(object
;; table behaviors
((TABLE? self) #t)
((SIZE self) (size table))
((PRINT self port) (format port "#<SIMPLE-TABLE>"))
((LOOKUP self key failure-object)
(cond
((assq key table) => cdr)
(else failure-object)
))
((ASSOCIATE! self key value)
(cond
((assq key table)
=> (lambda (bucket) (set-cdr! bucket value) key))
(else
(set! table (cons (cons key value) table))
key)
))
((REMOVE! self key);; returns old value
(cond
((null? table) (slib:error "TABLE:REMOVE! Key not found: " key))
((eq? key (caar table))
(let ( (value (cdar table)) )
(set! table (cdr table))
value)
)
(else
(let loop ( (last table) (this (cdr table)) )
(cond
((null? this)
(slib:error "TABLE:REMOVE! Key not found: " key))
((eq? key (caar this))
(let ( (value (cdar this)) )
(set-cdr! last (cdr this))
value)
)
(else
(loop (cdr last) (cdr this)))
) ) )
))
;; collection behaviors
((COLLECTION? self) #t)
((GEN-KEYS self) (collect:list-gen-elts (map car table)))
((GEN-ELTS self) (collect:list-gen-elts (map cdr table)))
((FOR-EACH-KEY self proc)
(for-each (lambda (bucket) (proc (car bucket))) table)
)
((FOR-EACH-ELT self proc)
(for-each (lambda (bucket) (proc (cdr bucket))) table)
)
) ) )
(require 'dynamic)
dynamic? satisfies any of the other standard type
predicates.
The dynamic-bind macro is not implemented.
(require 'hash-table)
hashq, hashv, or
hash) corresponding to the equality predicate pred.
pred should be eq?, eqv?, equal?, =,
char=?, char-ci=?, string=?, or
string-ci=?.A hash table is a vector of association lists.
Hash table functions provide utilities for an associative database.
These functions take an equality predicate, pred, as an argument.
pred should be eq?, eqv?, equal?, =,
char=?, char-ci=?, string=?, or
string-ci=?.
#f if no key in hashtab is pred-equal to
the first argument.
hashtab and key, which
returns the value associated with key in hashtab or
#f if key does not appear in hashtab.
(require 'hash)
These hashing functions are for use in quickly classifying objects. Hash tables use these functions.
For hashq, (eq? obj1 obj2) implies (= (hashq obj1 k)
(hashq obj2)).
For hashv, (eqv? obj1 obj2) implies (= (hashv obj1 k)
(hashv obj2)).
For hash, (equal? obj1 obj2) implies (= (hash obj1 k)
(hash obj2)).
hash, hashv, and hashq return in time bounded by a
constant. Notice that items having the same hash implies the
items have the same hashv implies the items have the same
hashq.
(require 'sierpinski)
max-coordinate is the maximum coordinate (a positive integer) of a population of points. The returned procedures is a function that takes the x and y coordinates of a point, (non-negative integers) and returns an integer corresponding to the relative position of that point along a Sierpinski curve. (You can think of this as computing a (pseudo-) inverse of the Sierpinski spacefilling curve.)
Example use: Make an indexer (hash-function) for integer points lying in square of integer grid points [0,99]x[0,99]:
(define space-key (make-sierpinski-indexer 100))
Now let's compute the index of some points:
(space-key 24 78) => 9206 (space-key 23 80) => 9172
Note that locations (24, 78) and (23, 80) are near in index and therefore, because the Sierpinski spacefilling curve is continuous, we know they must also be near in the plane. Nearness in the plane does not, however, necessarily correspond to nearness in index, although it tends to be so.
Example applications:
(require 'soundex)
Soundex was a classic algorithm used for manual filing of personal records before the advent of computers. It performs adequately for English names but has trouble with other nationalities.
See Knuth, Vol. 3 Sorting and searching, pp 391--2
To manage unusual inputs, soundex omits all non-alphabetic
characters. Consequently, in this implementation:
(soundex <string of blanks>) => "" (soundex "") => ""
Examples from Knuth:
(map soundex '("Euler" "Gauss" "Hilbert" "Knuth"
"Lloyd" "Lukasiewicz"))
=> ("E460" "G200" "H416" "K530" "L300" "L222")
(map soundex '("Ellery" "Ghosh" "Heilbronn" "Kant"
"Ladd" "Lissajous"))
=> ("E460" "G200" "H416" "K530" "L300" "L222")
Some cases in which the algorithm fails (Knuth):
(map soundex '("Rogers" "Rodgers")) => ("R262" "R326")
(map soundex '("Sinclair" "St. Clair")) => ("S524" "S324")
(map soundex '("Tchebysheff" "Chebyshev")) => ("T212" "C121")
(require 'chapter-order)
The `chap:' functions deal with strings which are ordered like chapter numbers (or letters) in a book. Each section of the string consists of consecutive numeric or consecutive aphabetic characters of like case.
string<? than the corresponding non-matching run of characters of
string2.
(chap:string<? "a.9" "a.10") => #t
(chap:string<? "4c" "4aa") => #t
(chap:string<? "Revised^{3.99}" "Revised^{4}") => #t
(string-append string "0") is returnd. The argument to
chap:next-string will always be chap:string<? than the result.
(chap:next-string "a.9") => "a.10"
(chap:next-string "4c") => "4d"
(chap:next-string "4z") => "4aa"
(chap:next-string "Revised^{4}") => "Revised^{5}"
(require 'object)
This is the Macroless Object System written by Wade Humeniuk (whumeniu@datap.ca). Conceptual Tributes: section Yasos, MacScheme's %object, CLOS, Lack of R4RS macros.
eq?) of methods
(procedures). Methods can be added (make-method!), deleted
(unmake-method!) and retrieved (get-method). Objects may
inherit methods from other objects. The object binds to the environment
it was created in, allowing closures to be used to hide private
procedures and data.
eq?) object's method.
This allows scheme function style to be used for objects. The calling
scheme for using a generic method is (generic-method object param1
param2 ...).
#t.
get-method.
unmake-method!
will restore the object's previous association with the
generic-method. method must be a procedure.
(require 'object)
(define instantiate (make-generic-method))
(define (make-instance-object . ancestors)
(define self (apply make-object
(map (lambda (obj) (instantiate obj)) ancestors)))
(make-method! self instantiate (lambda (self) self))
self)
(define who (make-generic-method))
(define imigrate! (make-generic-method))
(define emigrate! (make-generic-method))
(define describe (make-generic-method))
(define name (make-generic-method))
(define address (make-generic-method))
(define members (make-generic-method))
(define society
(let ()
(define self (make-instance-object))
(define population '())
(make-method! self imigrate!
(lambda (new-person)
(if (not (eq? new-person self))
(set! population (cons new-person population)))))
(make-method! self emigrate!
(lambda (person)
(if (not (eq? person self))
(set! population
(comlist:remove-if (lambda (member)
(eq? member person))
population)))))
(make-method! self describe
(lambda (self)
(map (lambda (person) (describe person)) population)))
(make-method! self who
(lambda (self) (map (lambda (person) (name person))
population)))
(make-method! self members (lambda (self) population))
self))
(define (make-person %name %address)
(define self (make-instance-object society))
(make-method! self name (lambda (self) %name))
(make-method! self address (lambda (self) %address))
(make-method! self who (lambda (self) (name self)))
(make-method! self instantiate
(lambda (self)
(make-person (string-append (name self) "-son-of")
%address)))
(make-method! self describe
(lambda (self) (list (name self) (address self))))
(imigrate! self)
self)
Inheritance:
<inverter>::(<number> <description>)
Generic-methods
<inverter>::value => <number>::value
<inverter>::set-value! => <number>::set-value!
<inverter>::describe => <description>::describe
<inverter>::help
<inverter>::invert
<inverter>::inverter?
Inheritance
<number>::()
Slots
<number>::<x>
Generic Methods
<number>::value
<number>::set-value!
(require 'object)
(define value (make-generic-method (lambda (val) val)))
(define set-value! (make-generic-method))
(define invert (make-generic-method
(lambda (val)
(if (number? val)
(/ 1 val)
(error "Method not supported:" val)))))
(define noop (make-generic-method))
(define inverter? (make-generic-predicate))
(define describe (make-generic-method))
(define help (make-generic-method))
(define (make-number x)
(define self (make-object))
(make-method! self value (lambda (this) x))
(make-method! self set-value!
(lambda (this new-value) (set! x new-value)))
self)
(define (make-description str)
(define self (make-object))
(make-method! self describe (lambda (this) str))
(make-method! self help (lambda (this) "Help not available"))
self)
(define (make-inverter)
(define self (make-object
(make-number 1)
(make-description "A number which can be inverted")))
(define <value> (get-method self value))
(make-method! self invert (lambda (self) (/ 1 (<value> self))))
(make-predicate! self inverter?)
(unmake-method! self help)
(make-method! self help
(lambda (self)
(display "Inverter Methods:") (newline)
(display " (value inverter) ==> n") (newline)))
self)
;;;; Try it out
(define invert! (make-generic-method))
(define x (make-inverter))
(make-method! x invert! (lambda () (set-value! x (/ 1 (value x)))))
(value x) => 1
(set-value! x 33) => undefined
(invert! x) => undefined
(value x) => 1/33
(unmake-method! x invert!) => undefined
(invert! x) error--> ERROR: Method not supported: x
(require 'parameters)
Arguments to procedures in scheme are distinguished from each other by their position in the procedure call. This can be confusing when a procedure takes many arguments, many of which are not often used.
A parameter-list is a way of passing named information to a procedure. Procedures are also defined to set unused parameters to default values, check parameters, and combine parameter lists.
A parameter has the form (parameter-name value1
...). This format allows for more than one value per
parameter-name.
A parameter-list is a list of parameters, each with a different parameter-name.
parameter-list-ref returns the value of parameter
parameter-name of parameter-list.
make-parameter-list
which created parameter-list. For each non-false element of
expanders that procedure is mapped over the corresponding
parameter value and the returned parameter lists are merged into
parameter-list.
This process is repeated until parameter-list stops growing. The
value returned from parameter-list-expand is unspecified.
make-parameter-list which
created parameter-list. fill-empty-parameters returns a
new parameter-list with each empty parameter filled with the
corresponding default.
make-parameter-list
which created parameter-list.
check-parameters returns parameter-list if each check
of the corresponding parameter-list returns non-false. If some
check returns #f an error is signaled.
In the following procedures arities is a list of symbols. The
elements of arities can be:
single
optional
boolean
nary
nary1
single and boolean are converted to
the single value associated with them. The other arity types are
converted to lists of the value(s) of type types.
positions is a list of positive integers whose order matches the
order of the parameter-names in the call to
make-parameter-list which created parameter-list. The
integers specify in which argument position the corresponding parameter
should appear.
getopt. Longer
strings will be treated as long-named options (see section Getopt).
getopt->parameter-list, but converts argv to an
argument-list as specified by optnames, positions,
arities, types, defaults, checks, and
aliases.
These getopt functions can be used with SLIB relational
databases. For an example, See section Database Utilities.
(require 'priority-queue)
make-heap. If there are no items in
heap, an error is signaled.The algorithm for priority queues was taken from Introduction to Algorithms by T. Cormen, C. Leiserson, R. Rivest. 1989 MIT Press.
(require 'queue)
A queue is a list where elements can be added to both the front and rear, and removed from the front (i.e., they are what are often called dequeues). A queue may also be used like a stack.
#t if obj is a queue.
#t if the queue q is empty.
All of the following functions raise an error if the queue q is empty.
queue-pop! is used to suggest that the queue is being
used like a stack.
(require 'record)
The Record package provides a facility for user to define their own record data types.
make-record-type that created the type represented by rtd;
if the field-names argument is provided, it is an error if it
contains any duplicates or any symbols not in the default list.
make-record-type
that created the type represented by rtd.
make-record-type that created the type represented by
rtd.
record? may be true of any Scheme
value; of course, if it returns true for some particular value, then
record-type-descriptor is applicable to that value and returns an
appropriate descriptor.
record-predicate, the resulting predicate would return a true
value when passed the given record. Note that it is not necessarily the
case that the returned descriptor is the one that was passed to
record-constructor in the call that created the constructor
procedure that created the given record.
eqv? to the type-name argument given in
the call to make-record-type that created the type represented by
rtd.
equal? to the
field-names argument given in the call to make-record-type that
created the type represented by rtd.
A base table implementation using Scheme association lists is available
as the value of the identifier alist-table after doing:
(require 'alist-table)
Association list base tables are suitable for small databases and support all Scheme types when temporary and readable/writeable Scheme types when saved. I hope support for other base table implementations will be added in the future.
This rest of this section documents the interface for a base table implementation from which the section Relational Database package constructs a Relational system. It will be of interest primarily to those wishing to port or write new base-table implementations.
All of these functions are accessed through a single procedure by
calling that procedure with the symbol name of the operation. A
procedure will be returned if that operation is supported and #f
otherwise. For example:
(require 'alist-table) (define open-base (alist-table 'make-base)) make-base => *a procedure* (define foo (alist-table 'foo)) foo => #f
#f is returned.
Calling the close-base method on this database and possibly other
operations will cause filename to be written to. If
filename is #f a temporary, non-disk based database will be
created if such can be supported by the base table implelentation.
#t, this database will have methods capable of
effecting change to the database. If mutable? is #f, only
methods for inquiring the database will be available. If the database
cannot be opened as specified #f is returned.
Calling the close-base (and possibly other) method on a
mutable? database will cause filename to be written to.
close-database (and possibly other) method on lldb may
cause filename to be written to. If filename is #f
this database will be changed to a temporary, non-disk based database if
such can be supported by the underlying base table implelentation. If
the operations completed successfully, #t is returned.
Otherwise, #f is returned.
#f, no action is taken and #f is returned. If this
operation completes successfully, #t is returned. Otherwise,
#f is returned.
#t is returned. Otherwise, #f is returned.
#f. The base table can then be opened using (open-table
lldb base-id). The positive integer key-dimension is
the number of keys composed to make a primary-key for this table.
The list of symbols column-types describes the types of each
column.
open-table. catalog-id will be used as the base table for
the system catalog.
#f.
As with make-table, the positive integer key-dimension is
the number of keys composed to make a primary-key for this table.
The list of symbols column-types describes the types of each
column.
#t if the base table associated with base-id was
removed from the low level database lldb, and #f otherwise.
Any 2 arguments of the supported type passed to the returned function
which are not equal? must result in returned values which are not
equal?.
Any 2 lists of supported types (which must at least include symbols and
non-negative integers) passed to the returned function which are not
equal? must result in returned values which are not
equal?.
(make-list-keyifier key-dimension types).
This procedure returns a key which is equal? to the
column-numberth element of the list which was passed to create
combined-key. The list types must have at least
key-dimension elements.
(make-list-keyifier key-dimension types).
This procedure returns a list of keys which are elementwise
equal? to the list which was passed to create combined-key.
In the following functions, the key argument can always be assumed to be the value returned by a call to a keyify routine.
#f value if there is a row associated with
key in the table opened in handle and #f otherwise.
#f otherwise.
#t if symbol names a type allowed as a column value
by the implementation, and #f otherwise. At a minimum, an
implementation must support the types integer, symbol,
string, boolean, and base-id.
#t if symbol names a type allowed as a key value by
the implementation, and #f otherwise. At a minimum, an
implementation must support the types integer, and symbol.
integer
symbol
boolean
#t or #f.
base-id
open-table. The value of catalog-id must be an acceptable
base-id.
(require 'relational-database)
This package implements a database system inspired by the Relational Model (E. F. Codd, A Relational Model of Data for Large Shared Data Banks). An SLIB relational database implementation can be created from any section Base Table implementation.
Most nontrivial programs contain databases: Makefiles, configure scripts, file backup, calendars, editors, source revision control, CAD systems, display managers, menu GUIs, games, parsers, debuggers, profilers, and even error reporting are all rife with databases. Coding databases is such a common activity in programming that many may not be aware of how often they do it.
A database often starts as a dispatch in a program. The author, perhaps because of the need to make the dispatch configurable, the need for correlating dispatch in other routines, or because of changes or growth, devises a data structure to contain the information, a routine for interpreting that data structure, and perhaps routines for augmenting and modifying the stored data. The dispatch must be converted into this form and tested.
The programmer may need to devise an interactive program for enabling easy examination and modification of the information contained in this database. Often, in an attempt to foster modularity and avoid delays in release, intermediate file formats for the database information are devised. It often turns out that users prefer modifying these intermediate files with a text editor to using the interactive program in order to do operations (such as global changes) not forseen by the program's author.
In order to address this need, the concientous software engineer may even provide a scripting language to allow users to make repetitive database changes. Users will grumble that they need to read a large manual and learn yet another programming language (even if it almost has language "xyz" syntax) in order to do simple configuration.
All of these facilities need to be designed, coded, debugged, documented, and supported; often causing what was very simple in concept to become a major developement project.
This view of databases just outlined is somewhat the reverse of the view of the originators of the Relational Model of database abstraction. The relational model was devised to unify and allow interoperation of large multi-user databases running on diverse platforms. A fairly general purpose "Comprehensive Language" for database manipulations is mandated (but not specified) as part of the relational model for databases.
One aspect of the Relational Model of some importance is that the "Comprehensive Language" must be expressible in some form which can be stored in the database. This frees the programmer from having to make programs data-driven in order to use a database.
This package includes as one of its basic supported types Scheme
expressions. This type allows expressions as defined by the
Scheme standards to be stored in the database. Using slib:eval
retrieved expressions can be evaluated (in the top-level environment).
Scheme's lambda facilitates closure of environments, modularity,
etc. so that procedures (which could not be stored directly most
databases) can still be effectively retrieved. Since slib:eval
evaluates expressions in the top-level environment, built-in and user
defined procedures can be easily accessed by name.
This package's purpose is to standardize (through a common interface) database creation and usage in Scheme programs. The relational model's provision for inclusion of language expressions as data as well as the description (in tables, of course) of all of its tables assures that relational databases are powerful enough to assume the roles currently played by thousands of ad-hoc routines and data formats.
Such standardization to a relational-like model brings many benefits:
Returns a procedure implementing a relational database using the base-table-implementation.
All of the operations of a base table implementation are accessed
through a procedure defined by requireing that implementation.
Similarly, all of the operations of the relational database
implementation are accessed through the procedure returned by
make-relational-system. For instance, a new relational database
could be created from the procedure returned by
make-relational-system by:
(require 'alist-table)
(define relational-alist-system
(make-relational-system alist-table))
(define create-alist-database
(relational-alist-system 'create-database))
(define my-database
(create-alist-database "mydata.db"))
What follows are the descriptions of the methods available from
relational system returned by a call to make-relational-system.
Returns an open, nearly empty relational database associated with
filename. The only tables defined are the system catalog and
domain table. Calling the close-database method on this database
and possibly other operations will cause filename to be written
to. If filename is #f a temporary, non-disk based database
will be created if such can be supported by the underlying base table
implelentation. If the database cannot be created as specified
#f is returned. For the fields and layout of descriptor tables,
See section Catalog Representation
Returns an open relational database associated with filename. If
mutable? is #t, this database will have methods capable of
effecting change to the database. If mutable? is #f, only
methods for inquiring the database will be available. Calling the
close-database (and possibly other) method on a mutable?
database will cause filename to be written to. If the database
cannot be opened as specified #f is returned.
These are the descriptions of the methods available from an open relational database. A method is retrieved from a database by calling the database with the symbol name of the operation. For example:
(define my-database
(create-alist-database "mydata.db"))
(define telephone-table-desc
((my-database 'create-table) 'telephone-table-desc))
#t is returned. Otherwise, #f is returned.
close-database (and
possibly other) method on this database will cause filename to be
written to. If filename is #f this database will be
changed to a temporary, non-disk based database if such can be supported
by the underlying base table implelentation. If the operations
completed successfully, #t is returned. Otherwise, #f is
returned.
#t if table-name exists in the system catalog,
otherwise returns #f.
#f.
These methods will be present only in databases which are mutable?.
#f otherwise.
#f. For the fields and layout of descriptor tables,
See section Catalog Representation.
#f.
These are the descriptions of the methods available from an open relational table. A method is retrieved from a table by calling the table with the symbol name of the operation. For example:
(define telephone-table-desc
((my-database 'create-table) 'telephone-table-desc))
(require 'common-list-functions)
(define ndrp (telephone-table-desc 'row:insert))
(ndrp '(1 #t name #f string))
(ndrp '(2 #f telephone
(lambda (d)
(and (string? d) (> (string-length d) 2)
(every
(lambda (c)
(memv c '(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8 #\9
#\+ #\( #\ #\) #\-)))
(string->list d))))
string))
Operations on a single column of a table are retrieved by giving the column name as the second argument to the methods procedure. For example:
(define column-ids ((telephone-table-desc 'get* 'column-number)))
Some operations described below require primary key arguments. Primary keys arguments are denoted key1 key2 .... It is an error to call an operation for a table which takes primary key arguments with the wrong number of primary keys for that table.
The term row used below refers to a Scheme list of values (one for
each column) in the order specified in the descriptor (table) for this
table. Missing values appear as #f. Primary keys may not
be missing.
#f
otherwise.
#f otherwise.
#f otherwise.
Each database (in an implementation) has a system catalog which describes all the user accessible tables in that database (including itself).
The system catalog base table has the following fields. PRI
indicates a primary key for that table.
PRI table-name
column-limit the highest column number
coltab-name descriptor table name
bastab-id data base table identifier
user-integrity-rule
view-procedure A scheme thunk which, when called,
produces a handle for the view. coltab
and bastab are specified if and only if
view-procedure is not.
Descriptors for base tables (not views) are tables (pointed to by system catalog). Descriptor (base) tables have the fields:
PRI column-number sequential integers from 1
primary-key? boolean TRUE for primary key components
column-name
column-integrity-rule
domain-name
A primary key is any column marked as primary-key? in the
corresponding descriptor table. All the primary-key? columns
must have lower column numbers than any non-primary-key? columns.
Every table must have at least one primary key. Primary keys must be
sufficient to distinguish all rows from each other in the table. All of
the system defined tables have a single primary key.
This package currently supports tables having from 1 to 4 primary keys if there are non-primary columns, and any (natural) number if all columns are primary keys. If you need more than 4 primary keys, I would like to hear what you are doing!
A domain is a category describing the allowable values to occur in a column. It is described by a (base) table with the fields:
PRI domain-name
foreign-table
domain-integrity-rule
type-id
type-param
The type-id field value is a symbol. This symbol may be used by the underlying base table implementation in storing that field.
If the foreign-table field is non-#f then that field names
a table from the catalog. The values for that domain must match a
primary key of the table referenced by the type-param (or
#f, if allowed). This package currently does not support
composite foreign-keys.
The types for which support is planned are:
atom
symbol
string [<length>]
number [<base>]
money <currency>
date-time
boolean
foreign-key <table-name>
expression
virtual <expression>
Although `rdms.scm' is not large I found it very difficult to write (six rewrites). I am not aware of any other examples of a generalized relational system (although there is little new in CS). I left out several aspects of the Relational model in order to simplify the job. The major features lacking (which might be addressed portably) are views, transaction boundaries, and protection.
Protection needs a model for specifying priveledges. Given how operations are accessed from handles it should not be difficult to restrict table accesses to those allowed for that user.
The system catalog has a field called view-procedure. This
should allow a purely functional implementation of views. This will
work but is unsatisfying for views resulting from a selection
(subset of rows); for whole table operations it will not be possible to
reduce the number of keys scanned over when the selection is specified
only by an opaque procedure.
Transaction boundaries present the most intriguing area. Transaction boundaries are actually a feature of the "Comprehensive Language" of the Relational database and not of the database. Scheme would seem to provide the opportunity for an extremely clean semantics for transaction boundaries since the builtin procedures with side effects are small in number and easily identified.
These side-effect builtin procedures might all be portably redefined to versions which properly handled transactions. Compiled library routines would need to be recompiled as well. Many system extensions (delete-file, system, etc.) would also need to be redefined.
There are 2 scope issues that must be resolved for multiprocess transaction boundaries:
dynamic-wind would
provide a workable hook into process switching for many implementations.
(require 'database-utilities)
This enhancement wraps a utility layer on relational-database
which provides:
*commands*
table in database.
Also included are utilities which provide:
for any SLIB relational database.
*commands* table)
relational database (with base-table type base-table-type)
associated with filename.
open-database will attempt to deduce the correct
base-table-type. If the database can not be opened or if it lacks the
*commands* table, #f is returned.
The table *commands* in an enhanced relational-database has
the fields (with domains):
PRI name symbol
parameters parameter-list
procedure expression
documentation string
The parameters field is a foreign key (domain
parameter-list) of the *catalog-data* table and should
have the value of a table described by *parameter-columns*. This
parameter-list table describes the arguments suitable for passing
to the associated command. The intent of this table is to be of a form
such that different user-interfaces (for instance, pull-down menus or
plain-text queries) can operate from the same table. A
parameter-list table has the following fields:
PRI index uint
name symbol
arity parameter-arity
domain domain
default expression
documentation string
The arity field can take the values:
single
optional
boolean
#f
is substituted) is acceptable.
nary
nary1
The domain field specifies the domain which a parameter or
parameters in the indexth field must satisfy.
The default field is an expression whose value is either
#f or a procedure of no arguments which returns a parameter or
parameter list as appropriate. If the expression's value is #f
then no default is appropriate for this parameter. Note that since the
default procedure is called every time a default parameter is
needed for this column, sticky defaults can be implemented using
shared state with the domain-integrity-rule.
When an enhanced relational-database is called with a symbol which
matches a name in the *commands* table, the associated
procedure expression is evaluated and applied to the enhanced
relational-database. A procedure should then be returned which the user
can invoke on (optional) arguments.
The command *initialize* is special. If present in the
*commands* table, open-database or open-database!
will return the value of the *initialize* command. Notice that
arbitrary code can be run when the *initialize* procedure is
automatically applied to the enhanced relational-database.
Note also that if you wish to shadow or hide from the user
relational-database methods described in section Relational Database Operations, this can be done by a dispatch in the closure returned by
the *initialize* expression rather than by entries in the
*commands* table if it is desired that the underlying methods
remain accessible to code in the *commands* table.
name field of the command's parameter-table.
index field of the command's parameter-table.
arity field of the command's parameter-table. For a
description of arity see table above.
defaults field of the command's parameter-table.
nary arity
parameters.
(alias parameter-name). There can be
more than one alias per parameter-name.
For information about parameters, See section Parameter lists. Here is an
example of setting up a command with arguments and parsing those
arguments from a getopt style argument list (see section Getopt).
(require 'database-utilities)
(require 'parameters)
(require 'getopt)
(define my-rdb (create-database #f 'alist-table))
(define-tables my-rdb
'(foo-params
*parameter-columns*
*parameter-columns*
((1 first-argument single string "hithere" "first argument")
(2 flag boolean boolean #f "a flag")))
'(foo-pnames
((name string))
((parameter-index uint))
(("l" 1)
("a" 2)))
'(my-commands
((name symbol))
((parameters parameter-list)
(parameter-names parameter-name-translation)
(procedure expression)
(documentation string))
((foo
foo-params
foo-pnames
(lambda (rdb) (lambda (foo aflag) (print foo aflag)))
"test command arguments"))))
(define (dbutil:serve-command-line rdb command-table
command argc argv)
(set! argv (if (vector? argv) (vector->list argv) argv))
((make-command-server rdb command-table)
command
(lambda (comname comval options positions
arities types defaults dirs aliases)
(apply comval (getopt->arglist argc argv options positions
arities types defaults dirs aliases)))))
(define (test)
(set! *optind* 1)
(dbutil:serve-command-line
my-rdb 'my-commands 'foo 4 '("dummy" "-l" "foo" "-a")))
(test)
-|
"foo" #t
Some commands are defined in all extended relational-databases. The are called just like section Relational Database Operations.
(car domain-row) and
returns #t. Otherwise returns #f.
For the fields and layout of the domain table, See section Catalog Representation
(<name> <descriptor-name> <descriptor-name> <rows>)
or
(<name> <primary-key-fields> <other-fields> <rows>)
where <name> is the table name, <descriptor-name> is the symbol name of a descriptor table, <primary-key-fields> and <other-fields> describe the primary keys and other fields respectively, and <rows> is a list of data rows to be added to the table.
<primary-key-fields> and <other-fields> are lists of field descriptors of the form:
(<column-name> <domain>)
or
(<column-name> <domain> <column-integrity-rule>)
where <column-name> is the column name, <domain> is the domain
of the column, and <column-integrity-rule> is an expression whose
value is a procedure of one argument (and returns non-#f to
signal an error).
If <domain> is not a defined domain name and it matches the name of this table or an already defined (in one of spec-0 ...) single key field table, a foriegn-key domain will be created for it.
*reports* in the relational database rdb.
destination is a port, string, or symbol. If destination is
a:
Each row in the table *reports* has the fields:
format string. At the beginning and end of each page
respectively, format is called with this string and the (list of)
column-names of this table.
format string. For each row in the table, format is
called with this string and the row.
0 if a row's lines should not be broken over page
boundaries.
Each row in the table *printers* has the fields:
The report is prepared as follows:
Format (see section Format) is called with the header field
and the (list of) column-names of the table.
Format is called with the reporter field and (on
successive calls) each record in the natural order for the table. A
count is kept of the number of newlines output by format. When the
number of newlines to be output exceeds the number of lines per page,
the set of lines will be broken if there are more than
minimum-break left on this page and the number of lines for this
row is larger or equal to twice minimum-break.
Format is called with the footer field and the (list of)
column-names of the table. The footer field should not output a
newline.
The following example shows a new database with the name of `foo.db' being created with tables describing processor families and processor/os/compiler combinations.
The database command define-tables is defined to call
define-tables with its arguments. The database is also
configured to print `Welcome' when the database is opened. The
database is then closed and reopened.
(require 'database-utilities)
(define my-rdb (create-database "foo.db" 'alist-table))
(define-tables my-rdb
'(*commands*
((name symbol))
((parameters parameter-list)
(procedure expression)
(documentation string))
((define-tables
no-parameters
no-parameter-names
(lambda (rdb) (lambda specs (apply define-tables rdb specs)))
"Create or Augment tables from list of specs")
(*initialize*
no-parameters
no-parameter-names
(lambda (rdb) (display "Welcome") (newline) rdb)
"Print Welcome"))))
((my-rdb 'define-tables)
'(processor-family
((family atom))
((also-ran processor-family))
((m68000 #f)
(m68030 m68000)
(i386 8086)
(8086 #f)
(powerpc #f)))
'(platform
((name symbol))
((processor processor-family)
(os symbol)
(compiler symbol))
((aix powerpc aix -)
(amiga-dice-c m68000 amiga dice-c)
(amiga-aztec m68000 amiga aztec)
(amiga-sas/c-5.10 m68000 amiga sas/c)
(atari-st-gcc m68000 atari gcc)
(atari-st-turbo-c m68000 atari turbo-c)
(borland-c-3.1 8086 ms-dos borland-c)
(djgpp i386 ms-dos gcc)
(linux i386 linux gcc)
(microsoft-c 8086 ms-dos microsoft-c)
(os/2-emx i386 os/2 gcc)
(turbo-c-2 8086 ms-dos turbo-c)
(watcom-9.0 i386 ms-dos watcom))))
((my-rdb 'close-database))
(set! my-rdb (open-database "foo.db" 'alist-table))
-|
Welcome
(require 'wt-tree)
Balanced binary trees are a useful data structure for maintaining large sets of ordered objects or sets of associations whose keys are ordered. MIT Scheme has an comprehensive implementation of weight-balanced binary trees which has several advantages over the other data structures for large aggregates:
(+ 1 x)
modifies neither the constant 1 nor the value bound to x. The
trees are referentially transparent thus the programmer need not worry
about copying the trees. Referential transparency allows space
efficiency to be achieved by sharing subtrees.
These features make weight-balanced trees suitable for a wide range of applications, especially those that require large numbers of sets or discrete maps. Applications that have a few global databases and/or concentrate on element-level operations like insertion and lookup are probably better off using hash-tables or red-black trees.
The size of a tree is the number of associations that it contains. Weight balanced binary trees are balanced to keep the sizes of the subtrees of each node within a constant factor of each other. This ensures logarithmic times for single-path operations (like lookup and insertion). A weight balanced tree takes space that is proportional to the number of associations in the tree. For the current implementation, the constant of proportionality is six words per association.
Weight balanced trees can be used as an implementation for either
discrete sets or discrete maps (associations). Sets are implemented by
ignoring the datum that is associated with the key. Under this scheme
if an associations exists in the tree this indicates that the key of the
association is a member of the set. Typically a value such as
(), #t or #f is associated with the key.
Many operations can be viewed as computing a result that, depending on
whether the tree arguments are thought of as sets or maps, is known by
two different names.
An example is wt-tree/member?, which, when
regarding the tree argument as a set, computes the set membership operation, but,
when regarding the tree as a discrete map, wt-tree/member? is the
predicate testing if the map is defined at an element in its domain.
Most names in this package have been chosen based on interpreting the
trees as sets, hence the name wt-tree/member? rather than
wt-tree/defined-at?.
The weight balanced tree implementation is a run-time-loadable option. To use weight balanced trees, execute
(load-option 'wt-tree)
once before calling any of the procedures defined here.
Binary trees require there to be a total order on the keys used to arrange the elements in the tree. Weight balanced trees are organized by types, where the type is an object encapsulating the ordering relation. Creating a tree is a two-stage process. First a tree type must be created from the predicate which gives the ordering. The tree type is then used for making trees, either empty or singleton trees or trees from other aggregate structures like association lists. Once created, a tree `knows' its type and the type is used to test compatibility between trees in operations taking two trees. Usually a small number of tree types are created at the beginning of a program and used many times throughout the program's execution.
a, b and c:
(key<? a a) => #f
(and (key<? a b) (key<? b a)) => #f
(if (and (key<? a b) (key<? b c))
(key<? a c)
#t) => #t
Two key values are assumed to be equal if neither is less than the other by key<?.
Each call to make-wt-tree-type returns a distinct value, and
trees are only compatible if their tree types are eq?.
A consequence is
that trees that are intended to be used in binary tree operations must all be
created with a tree type originating from the same call to
make-wt-tree-type.
Number-wt-type
could have been defined by
(define number-wt-type (make-wt-tree-type <))
String-wt-type
could have been defined by
(define string-wt-type (make-wt-tree-type string<?))
make-wt-tree-type; the returned tree has this type.
make-wt-tree-type; the returned tree has this type.
(lambda (type alist)
(let ((tree (make-wt-tree type)))
(for-each (lambda (association)
(wt-tree/add! tree
(car association)
(cdr association)))
alist)
tree))
This section describes the basic tree operations on weight balanced trees. These operations are the usual tree operations for insertion, deletion and lookup, some predicates and a procedure for determining the number of associations in a tree.
#t if object is a weight-balanced tree, otherwise
returns #f.
#t if wt-tree contains no associations, otherwise
returns #f.
#t if wt-tree contains an association for
key, otherwise returns #f. The average and worst-case
times required by this operation are proportional to the logarithm of
the number of associations in wt-tree.
In the following the size of a tree is the number of associations that the tree contains, and a smaller tree contains fewer associations.
wt-tree/union computes the map override of wt-tree-1 by
wt-tree-2. If the trees are viewed as sets the result is the set
union of the arguments.
The worst-case time required by this operation
is proportional to the sum of the sizes of both trees.
If the minimum key of one tree is greater than the maximum key of
the other tree then the time required is at worst proportional to
the logarithm of the size of the larger tree.
wt-tree/intersection computes the domain restriction of
wt-tree-1 to (the domain of) wt-tree-2.
The time required by this operation is never worse that proportional to
the sum of the sizes of the trees.
#t iff the key of each association in wt-tree-1 is
the key of some association in wt-tree-2, otherwise returns #f.
Viewed as a set operation, wt-tree/subset? is the improper subset
predicate.
A proper subset predicate can be constructed:
(define (proper-subset? s1 s2)
(and (wt-tree/subset? s1 s2)
(< (wt-tree/size s1) (wt-tree/size s2))))
As a discrete map operation, wt-tree/subset? is the subset
test on the domain(s) of the map(s). In the worst-case the time
required by this operation is proportional to the size of
wt-tree-1.
#t iff for every association in wt-tree-1 there is
an association in wt-tree-2 that has the same key, and vice
versa.
Viewing the arguments as sets wt-tree/set-equal? is the set
equality predicate. As a map operation it determines if two maps are
defined on the same domain.
This procedure is equivalent to
(lambda (wt-tree-1 wt-tree-2)
(and (wt-tree/subset? wt-tree-1 wt-tree-2
(wt-tree/subset? wt-tree-2 wt-tree-1)))
In the worst-case the time required by this operation is proportional to the size of the smaller tree.
wt-tree/fold takes time
proportional to the size of wt-tree.
A sorted association list can be derived simply:
(wt-tree/fold (lambda (key datum list)
(cons (cons key datum) list))
'()
wt-tree))
The data in the associations can be summed like this:
(wt-tree/fold (lambda (key datum sum) (+ sum datum))
0
wt-tree)
wt-tree/for-each takes time proportional to in the size of
wt-tree.
The example prints the tree:
(wt-tree/for-each (lambda (key value)
(display (list key value)))
wt-tree))
Weight balanced trees support operations that view the tree as sorted sequence of associations. Elements of the sequence can be accessed by position, and the position of an element in the sequence can be determined, both in logarthmic time.
wt-tree/index returns the indexth key,
wt-tree/index-datum returns the datum associated with the
indexth key and wt-tree/index-pair returns a new pair
(key . datum) which is the cons of the indexth
key and its datum. The average and worst-case times required by this
operation are proportional to the logarithm of the number of
associations in the tree.
These operations signal an error if the tree is empty, if
index<0, or if index is greater than or equal to the
number of associations in the tree.
Indexing can be used to find the median and maximum keys in the tree as follows:
median: (wt-tree/index wt-tree (quotient (wt-tree/size wt-tree) 2)) maximum: (wt-tree/index wt-tree (-1+ (wt-tree/size wt-tree)))
#f if the tree
has no association with for key. This procedure returns either an
exact non-negative integer or #f. The average and worst-case
times required by this operation are proportional to the logarithm of
the number of associations in the tree.
wt-tree/min returns the least key,
wt-tree/min-datum returns the datum associated with the
least key and wt-tree/min-pair returns a new pair
(key . datum) which is the cons of the minimum key and its datum.
The average and worst-case times required by this operation are
proportional to the logarithm of the number of associations in the tree.
These operations signal an error if the tree is empty. They could be written
(define (wt-tree/min tree) (wt-tree/index tree 0)) (define (wt-tree/min-datum tree) (wt-tree/index-datum tree 0)) (define (wt-tree/min-pair tree) (wt-tree/index-pair tree 0))
(wt-tree/delete wt-tree (wt-tree/min wt-tree))
(wt-tree/delete! wt-tree (wt-tree/min wt-tree))
(require 'struct) (uses defmacros)
defmacros which implement records from the book
Essentials of Programming Languages by Daniel P. Friedman, M.
Wand and C.T. Haynes. Copyright 1992 Jeff Alexander, Shinnder Lee, and
Lewis Patterson
Matthew McDonald <mafm@cs.uwa.edu.au> added field setters.
Here is an example of its use.
(define-record term (operator left right)) => #<unspecified> (define foo (make-term 'plus 1 2)) => foo (term-left foo) => 1 (set-term-left! foo 2345) => #<unspecified> (term-left foo) => 2345
((lambda (var1 var ...) body) (tag->var1 exp) (tag->var2 exp) ...)
Defmacros are supported by all implementations.
(gentemp) => scm:G0 (gentemp) => scm:G1
slib:eval of expanding all defmacros in scheme
expression e.
defmacro:load procedure reads Scheme source code expressions
and definitions from the file and evaluates them sequentially. These
source code expressions and definitions may contain defmacro
definitions. The macro:load procedure does not affect the values
returned by current-input-port and
current-output-port.
#t if sym has been defined by defmacro,
#f otherwise.
macroexpand-1 will expand the
macro call once and return it. A form is considered to be a macro
call only if it is a cons whose car is a symbol for which a
defmacr has been defined.
macroexpand is similar to macroexpand-1, but repeatedly
expands form until it is no longer a macro call.
defmacro:eval, defmacro:macroexpand*,
or defmacro:load defines a new macro which will henceforth be
expanded when encountered by defmacro:eval,
defmacro:macroexpand*, or defmacro:load.
(require 'defmacroexpand)
(require 'macro) is the appropriate call if you want R4RS
high-level macros but don't care about the low level implementation. If
an SLIB R4RS macro implementation is already loaded it will be used.
Otherwise, one of the R4RS macros implemetations is loaded.
The SLIB R4RS macro implementations support the following uniform interface:
macro:load procedure reads Scheme source code expressions and
definitions from the file and evaluates them sequentially. These source
code expressions and definitions may contain macro definitions. The
macro:load procedure does not affect the values returned by
current-input-port and current-output-port.
(require 'macro-by-example)
A vanilla implementation of Macro by Example (Eugene Kohlbecker,
R4RS) by Dorai Sitaram, (dorai@cs.rice.edu) using defmacro.
define-syntax Macro-by-Example macros
cheaply.
....
defmacro
natively supported (most implementations)
These macros are not referentially transparent (see section `Macros' in Revised(4) Scheme). Lexically scoped macros (i.e., let-syntax
and letrec-syntax) are not supported. In any case, the problem
of referential transparency gains poignancy only when let-syntax
and letrec-syntax are used. So you will not be courting
large-scale disaster unless you're using system-function names as local
variables with unintuitive bindings that the macro can't use. However,
if you must have the full r4rs macro functionality, look to the
more featureful (but also more expensive) versions of syntax-rules
available in slib section Macros That Work, section Syntactic Closures, and
section Syntax-Case Macros.
syntax-rules.
The top-level syntactic environment is extended by binding the keyword to the specified transformer.
(define-syntax let*
(syntax-rules ()
((let* () body1 body2 ...)
(let () body1 body2 ...))
((let* ((name1 val1) (name2 val2) ...)
body1 body2 ...)
(let ((name1 val1))
(let* (( name2 val2) ...)
body1 body2 ...)))))
(pattern template)
where the pattern and template are as in the grammar above.
An instance of syntax-rules produces a new macro transformer by
specifying a sequence of hygienic rewrite rules. A use of a macro whose
keyword is associated with a transformer specified by
syntax-rules is matched against the patterns contained in the
syntax-rules, beginning with the leftmost syntax-rule.
When a match is found, the macro use is trancribed hygienically
according to the template.
Each pattern begins with the keyword for the macro. This keyword is not involved in the matching and is not considered a pattern variable or literal identifier.
(require 'macros-that-work)
Macros That Work differs from the other R4RS macro implementations in that it does not expand derived expression types to primitive expression types.
macro:eval returns the value of expression in the current
top level environment. expression can contain macro definitions.
Side effects of expression will affect the top level
environment.
macro:load procedure reads Scheme source code expressions and
definitions from the file and evaluates them sequentially. These source
code expressions and definitions may contain macro definitions. The
macro:load procedure does not affect the values returned by
current-input-port and current-output-port.References:
The Revised^4 Report on the Algorithmic Language Scheme Clinger and Rees [editors]. To appear in LISP Pointers. Also available as a technical report from the University of Oregon, MIT AI Lab, and Cornell.
Macros That Work. Clinger and Rees. POPL '91.
The supported syntax differs from the R4RS in that vectors are allowed as patterns and as templates and are not allowed as pattern or template data.
transformer spec ==> (syntax-rules literals rules)
rules ==> ()
| (rule . rules)
rule ==> (pattern template)
pattern ==> pattern_var ; a symbol not in literals
| symbol ; a symbol in literals
| ()
| (pattern . pattern)
| (ellipsis_pattern)
| #(pattern*) ; extends R4RS
| #(pattern* ellipsis_pattern) ; extends R4RS
| pattern_datum
template ==> pattern_var
| symbol
| ()
| (template2 . template2)
| #(template*) ; extends R4RS
| pattern_datum
template2 ==> template
| ellipsis_template
pattern_datum ==> string ; no vector
| character
| boolean
| number
ellipsis_pattern ==> pattern ...
ellipsis_template ==> template ...
pattern_var ==> symbol ; not in literals
literals ==> ()
| (symbol . literals)
...) is
the pattern or template that appears to its left.
No pattern variable appears more than once within a pattern.
For every occurrence of a pattern variable within a template, the template rank of the occurrence must be greater than or equal to the pattern variable's rank.
Every ellipsis template must open at least one variable.
For every ellipsis template, the variables opened by an ellipsis template must all be bound to sequences of the same length.
The compiled form of a rule is
rule ==> (pattern template inserted)
pattern ==> pattern_var
| symbol
| ()
| (pattern . pattern)
| ellipsis_pattern
| #(pattern)
| pattern_datum
template ==> pattern_var
| symbol
| ()
| (template2 . template2)
| #(pattern)
| pattern_datum
template2 ==> template
| ellipsis_template
pattern_datum ==> string
| character
| boolean
| number
pattern_var ==> #(V symbol rank)
ellipsis_pattern ==> #(E pattern pattern_vars)
ellipsis_template ==> #(E template pattern_vars)
inserted ==> ()
| (symbol . inserted)
pattern_vars ==> ()
| (pattern_var . pattern_vars)
rank ==> exact non-negative integer
where V and E are unforgeable values.
The pattern variables associated with an ellipsis pattern are the variables bound by the pattern, and the pattern variables associated with an ellipsis template are the variables opened by the ellipsis template.
If the template contains a big chunk that contains no pattern variables or inserted identifiers, then the big chunk will be copied unnecessarily. That shouldn't matter very often.
(require 'syntactic-closures)
macro:eval returns the value of expression in the current
top level environment. expression can contain macro definitions.
Side effects of expression will affect the top level
environment.
macro:load procedure reads Scheme source code expressions and
definitions from the file and evaluates them sequentially. These
source code expressions and definitions may contain macro definitions.
The macro:load procedure does not affect the values returned by
current-input-port and current-output-port.A Syntactic Closures Macro Facility by Chris Hanson 9 November 1991
This document describes syntactic closures, a low-level macro facility for the Scheme programming language. The facility is an alternative to the low-level macro facility described in the Revised^4 Report on Scheme. This document is an addendum to that report.
The syntactic closures facility extends the BNF rule for transformer spec to allow a new keyword that introduces a low-level macro transformer:
transformer spec := (transformer expression)
Additionally, the following procedures are added:
make-syntactic-closure capture-syntactic-environment identifier? identifier=?
The description of the facility is divided into three parts. The first
part defines basic terminology. The second part describes how macro
transformers are defined. The third part describes the use of
identifiers, which extend the syntactic closure mechanism to be
compatible with syntax-rules.
This section defines the concepts and data types used by the syntactic closures facility.
set! special form is also a form. Examples of
forms:
17 #t car (+ x 4) (lambda (x) x) (define pi 3.14159) if define
symbol?. Macro transformers rarely distinguish symbols from
aliases, referring to both as identifiers.
This section describes the transformer special form and the
procedures make-syntactic-closure and
capture-syntactic-environment.
Syntax: It is an error if this syntax occurs except as a transformer spec.
Semantics: The expression is evaluated in the standard transformer
environment to yield a macro transformer as described below. This macro
transformer is bound to a macro keyword by the special form in which the
transformer expression appears (for example,
let-syntax).
A macro transformer is a procedure that takes two arguments, a
form and a syntactic environment, and returns a new form. The first
argument, the input form, is the form in which the macro keyword
occurred. The second argument, the usage environment, is the
syntactic environment in which the input form occurred. The result of
the transformer, the output form, is automatically closed in the
transformer environment, which is the syntactic environment in
which the transformer expression occurred.
For example, here is a definition of a push macro using
syntax-rules:
(define-syntax push
(syntax-rules ()
((push item list)
(set! list (cons item list)))))
Here is an equivalent definition using transformer:
(define-syntax push
(transformer
(lambda (exp env)
(let ((item
(make-syntactic-closure env '() (cadr exp)))
(list
(make-syntactic-closure env '() (caddr exp))))
`(set! ,list (cons ,item ,list))))))
In this example, the identifiers set! and cons are closed
in the transformer environment, and thus will not be affected by the
meanings of those identifiers in the usage environment
env.
Some macros may be non-hygienic by design. For example, the following
defines a loop macro that implicitly binds exit to an escape
procedure. The binding of exit is intended to capture free
references to exit in the body of the loop, so exit must
be left free when the body is closed:
(define-syntax loop
(transformer
(lambda (exp env)
(let ((body (cdr exp)))
`(call-with-current-continuation
(lambda (exit)
(let f ()
,@(map (lambda (exp)
(make-syntactic-closure env '(exit)
exp))
body)
(f))))))))
To assign meanings to the identifiers in a form, use
make-syntactic-closure to close the form in a syntactic
environment.
environment must be a syntactic environment, free-names must
be a list of identifiers, and form must be a form.
make-syntactic-closure constructs and returns a syntactic closure
of form in environment, which can be used anywhere that
form could have been used. All the identifiers used in
form, except those explicitly excepted by free-names, obtain
their meanings from environment.
Here is an example where free-names is something other than the
empty list. It is instructive to compare the use of free-names in
this example with its use in the loop example above: the examples
are similar except for the source of the identifier being left
free.
(define-syntax let1
(transformer
(lambda (exp env)
(let ((id (cadr exp))
(init (caddr exp))
(exp (cadddr exp)))
`((lambda (,id)
,(make-syntactic-closure env (list id) exp))
,(make-syntactic-closure env '() init))))))
let1 is a simplified version of let that only binds a
single identifier, and whose body consists of a single expression. When
the body expression is syntactically closed in its original syntactic
environment, the identifier that is to be bound by let1 must be
left free, so that it can be properly captured by the lambda in
the output form.
To obtain a syntactic environment other than the usage environment, use
capture-syntactic-environment.
capture-syntactic-environment returns a form that will, when
transformed, call procedure on the current syntactic environment.
procedure should compute and return a new form to be transformed,
in that same syntactic environment, in place of the form.
An example will make this clear. Suppose we wanted to define a simple
loop-until keyword equivalent to
(define-syntax loop-until
(syntax-rules ()
((loop-until id init test return step)
(letrec ((loop
(lambda (id)
(if test return (loop step)))))
(loop init)))))
The following attempt at defining loop-until has a subtle bug:
(define-syntax loop-until
(transformer
(lambda (exp env)
(let ((id (cadr exp))
(init (caddr exp))
(test (cadddr exp))
(return (cadddr (cdr exp)))
(step (cadddr (cddr exp)))
(close
(lambda (exp free)
(make-syntactic-closure env free exp))))
`(letrec ((loop
(lambda (,id)
(if ,(close test (list id))
,(close return (list id))
(loop ,(close step (list id)))))))
(loop ,(close init '())))))))
This definition appears to take all of the proper precautions to prevent
unintended captures. It carefully closes the subexpressions in their
original syntactic environment and it leaves the id identifier
free in the test, return, and step expressions, so
that it will be captured by the binding introduced by the lambda
expression. Unfortunately it uses the identifiers if and
loop within that lambda expression, so if the user of
loop-until just happens to use, say, if for the
identifier, it will be inadvertently captured.
The syntactic environment that if and loop want to be
exposed to is the one just outside the lambda expression: before
the user's identifier is added to the syntactic environment, but after
the identifier loop has been added.
capture-syntactic-environment captures exactly that environment
as follows:
(define-syntax loop-until
(transformer
(lambda (exp env)
(let ((id (cadr exp))
(init (caddr exp))
(test (cadddr exp))
(return (cadddr (cdr exp)))
(step (cadddr (cddr exp)))
(close
(lambda (exp free)
(make-syntactic-closure env free exp))))
`(letrec ((loop
,(capture-syntactic-environment
(lambda (env)
`(lambda (,id)
(,(make-syntactic-closure env '() `if)
,(close test (list id))
,(close return (list id))
(,(make-syntactic-closure env '()
`loop)
,(close step (list id)))))))))
(loop ,(close init '())))))))
In this case, having captured the desired syntactic environment, it is
convenient to construct syntactic closures of the identifiers if
and the loop and use them in the body of the
lambda.
A common use of capture-syntactic-environment is to get the
transformer environment of a macro transformer:
(transformer
(lambda (exp env)
(capture-syntactic-environment
(lambda (transformer-env)
...))))
This section describes the procedures that create and manipulate
identifiers. Previous syntactic closure proposals did not have an
identifier data type -- they just used symbols. The identifier data
type extends the syntactic closures facility to be compatible with the
high-level syntax-rules facility.
As discussed earlier, an identifier is either a symbol or an alias. An alias is implemented as a syntactic closure whose form is an identifier:
(make-syntactic-closure env '() 'a) => an alias
Aliases are implemented as syntactic closures because they behave just
like syntactic closures most of the time. The difference is that an
alias may be bound to a new value (for example by lambda or
let-syntax); other syntactic closures may not be used this way.
If an alias is bound, then within the scope of that binding it is looked
up in the syntactic environment just like any other identifier.
Aliases are used in the implementation of the high-level facility
syntax-rules. A macro transformer created by syntax-rules
uses a template to generate its output form, substituting subforms of
the input form into the template. In a syntactic closures
implementation, all of the symbols in the template are replaced by
aliases closed in the transformer environment, while the output form
itself is closed in the usage environment. This guarantees that the
macro transformation is hygienic, without requiring the transformer to
know the syntactic roles of the substituted input subforms.
#t if object is an identifier, otherwise returns
#f. Examples:
(identifier? 'a) => #t (identifier? (make-syntactic-closure env '() 'a)) => #t (identifier? "a") => #f (identifier? #\a) => #f (identifier? 97) => #f (identifier? #f) => #f (identifier? '(a)) => #f (identifier? '#(a)) => #f
The predicate eq? is used to determine if two identifers are
"the same". Thus eq? can be used to compare identifiers
exactly as it would be used to compare symbols. Often, though, it is
useful to know whether two identifiers "mean the same thing". For
example, the cond macro uses the symbol else to identify
the final clause in the conditional. A macro transformer for
cond cannot just look for the symbol else, because the
cond form might be the output of another macro transformer that
replaced the symbol else with an alias. Instead the transformer
must look for an identifier that "means the same thing" in the usage
environment as the symbol else means in the transformer
environment.
identifier=? returns #t if the meaning of
identifier1 in environment1 is the same as that of
identifier2 in environment2, otherwise it returns #f.
Examples:
(let-syntax
((foo
(transformer
(lambda (form env)
(capture-syntactic-environment
(lambda (transformer-env)
(identifier=? transformer-env 'x env 'x)))))))
(list (foo)
(let ((x 3))
(foo))))
=> (#t #f)
(let-syntax ((bar foo))
(let-syntax
((foo
(transformer
(lambda (form env)
(capture-syntactic-environment
(lambda (transformer-env)
(identifier=? transformer-env 'foo
env (cadr form))))))))
(list (foo foo)
(foobar))))
=> (#f #t)
The syntactic closures facility was invented by Alan Bawden and Jonathan
Rees. The use of aliases to implement syntax-rules was invented
by Alan Bawden (who prefers to call them synthetic names). Much
of this proposal is derived from an earlier proposal by Alan
Bawden.
(require 'syntax-case)
macro:eval returns the value of expression in the current
top level environment. expression can contain macro definitions.
Side effects of expression will affect the top level
environment.
macro:load procedure reads Scheme source code expressions and
definitions from the file and evaluates them sequentially. These
source code expressions and definitions may contain macro definitions.
The macro:load procedure does not affect the values returned by
current-input-port and current-output-port.
This is version 2.1 of syntax-case, the low-level macro facility
proposed and implemented by Robert Hieb and R. Kent Dybvig.
This version is further adapted by Harald Hanche-Olsen <hanche@imf.unit.no> to make it compatible with, and easily usable with, SLIB. Mainly, these adaptations consisted of:
If you wish, you can see exactly what changes were done by reading the shell script in the file `syncase.sh'.
The two PostScript files were omitted in order to not burden the SLIB
distribution with them. If you do intend to use syntax-case,
however, you should get these files and print them out on a PostScript
printer. They are available with the original syntax-case
distribution by anonymous FTP in
`cs.indiana.edu:/pub/scheme/syntax-case'.
In order to use syntax-case from an interactive top level, execute:
(require 'syntax-case) (require 'repl) (repl:top-level macro:eval)
See the section Repl (See section Repl) for more information.
To check operation of syntax-case get `cs.indiana.edu:/pub/scheme/syntax-case', and type
(require 'syntax-case) (syncase:sanity-check)
Beware that syntax-case takes a long time to load -- about 20s on
a SPARCstation SLC (with SCM) and about 90s on a Macintosh SE/30 (with
Gambit).
All R4RS syntactic forms are defined, including delay. Along
with delay are simple definitions for make-promise (into
which delay expressions expand) and force.
syntax-rules and with-syntax (described in TR356)
are defined.
syntax-case is actually defined as a macro that expands into
calls to the procedure syntax-dispatch and the core form
syntax-lambda; do not redefine these names.
Several other top-level bindings not documented in TR356 are created:
build- procedures in `output.ss'
expand-syntax (the expander)
The syntax of define has been extended to allow (define id),
which assigns id to some unspecified value.
We have attempted to maintain R4RS compatibility where possible. The incompatibilities should be confined to `hooks.ss'. Please let us know if there is some incompatibility that is not flagged as such.
Send bug reports, comments, suggestions, and questions to Kent Dybvig (dyb@iuvax.cs.indiana.edu).
Included with the syntax-case files was `structure.scm'
which defines a macro define-structure. There is no
documentation for this macro and it is not used by any code in SLIB.
(require 'fluid-let)
(bindings ...) forms...
(fluid-let ((variable init) ...) expression expression ...)
The inits are evaluated in the current environment (in some unspecified order), the current values of the variables are saved, the results are assigned to the variables, the expressions are evaluated sequentially in the current environment, the variables are restored to their original values, and the value of the last expression is returned.
The syntax of this special form is similar to that of let, but
fluid-let temporarily rebinds existing variables. Unlike
let, fluid-let creates no new bindings; instead it
assigns the values of each init to the binding (determined
by the rules of lexical scoping) of its corresponding
variable.
(require 'oop) or (require 'yasos)
`Yet Another Scheme Object System' is a simple object system for Scheme based on the paper by Norman Adams and Jonathan Rees: Object Oriented Programming in Scheme, Proceedings of the 1988 ACM Conference on LISP and Functional Programming, July 1988 [ACM #552880].
Another reference is:
Ken Dickey. Scheming with Objects AI Expert Volume 7, Number 10 (October 1992), pp. 24-33.
let). An
operation may be applied to any Scheme data object--not just instances.
As code which creates instances is just code, there are no classes
and no meta-anything. Method dispatch is by a procedure call a la
CLOS rather than by send syntax a la Smalltalk.
(opname self arg ...) default-body
(opname? object)
returns #t if object has an operation opname? and
#f otherwise.
((name self arg ...) body) ...
(name object arg ... executes the
body of the object with self bound to object and
with argument(s) arg....
((ancestor1 init1) ...) operation ...
let-like form of object for multiple inheritance. It
returns an object inheriting the behaviour of ancestor1 etc. An
operation will be invoked in an ancestor if the object itself does not
provide such a method. In the case of multiple inherited operations
with the same identity, the operation used is the one found in the first
ancestor in the ancestor list.
print operation is provided which is just (format
port obj) (See section Format) for non-instances and prints
obj preceded by `#<INSTANCE>' for instances.
2 for a pair, 1 for a character
and by default id an error otherwise. Objects such as collections
(See section Collections) may override the default in an obvious way.
Setters implement generalized locations for objects
associated with some sort of mutable state. A getter operation
retrieves a value from a generalized location and the corresponding
setter operation stores a value into the location. Only the getter is
named -- the setter is specified by a procedure call as below. (Dylan
uses special syntax.) Typically, but not necessarily, getters are
access operations to extract values from Yasos objects (See section Yasos).
Several setters are predefined, corresponding to getters car,
cdr, string-ref and vector-ref e.g., (setter
car) is equivalent to set-car!.
This implementation of setters is similar to that in Dylan(TM)
(Dylan: An object-oriented dynamic language, Apple Computer
Eastern Research and Technology). Common LISP provides similar
facilities through setf.
string-ref is the getter corresponding to a setter which is
actually string-set!:
(define foo "foo") ((setter string-ref) foo 0 #\F) ; set element 0 of foo foo => "Foo"
set is equivalent to
set!. Otherwise, place must have the form of a procedure
call, where the procedure name refers to a getter and the call indicates
an accessible generalized location, i.e., the call would return a value.
The return value of set is usually unspecified unless used with a
setter whose definition guarantees to return a useful value.
(set (string-ref foo 2) #\O) ; generalized location with getter foo => "FoO" (set foo "foo") ; like set! foo => "foo"
define-operation defining an operation
getter-name that objects may support to return the value of some
mutable state. The default operation is to signal an error. The return
value is unspecified.
(define-operation (print obj port)
(format port
(if (instance? obj) "#<instance>" "~s")
obj))
(define-operation (SIZE obj)
(cond
((vector? obj) (vector-length obj))
((list? obj) (length obj))
((pair? obj) 2)
((string? obj) (string-length obj))
((char? obj) 1)
(else
(error "Operation not supported: size" obj))))
(define-predicate cell?)
(define-operation (fetch obj))
(define-operation (store! obj newValue))
(define (make-cell value)
(object
((cell? self) #t)
((fetch self) value)
((store! self newValue)
(set! value newValue)
newValue)
((size self) 1)
((print self port)
(format port "#<Cell: ~s>" (fetch self)))))
(define-operation (discard obj value)
(format #t "Discarding ~s~%" value))
(define (make-filtered-cell value filter)
(object-with-ancestors ((cell (make-cell value)))
((store! self newValue)
(if (filter newValue)
(store! cell newValue)
(discard self newValue)))))
(define-predicate array?)
(define-operation (array-ref array index))
(define-operation (array-set! array index value))
(define (make-array num-slots)
(let ((anArray (make-vector num-slots)))
(object
((array? self) #t)
((size self) num-slots)
((array-ref self index) (vector-ref anArray index))
((array-set! self index newValue) (vector-set! anArray index newValue))
((print self port) (format port "#<Array ~s>" (size self))))))
(define-operation (position obj))
(define-operation (discarded-value obj))
(define (make-cell-with-history value filter size)
(let ((pos 0) (most-recent-discard #f))
(object-with-ancestors
((cell (make-filtered-call value filter))
(sequence (make-array size)))
((array? self) #f)
((position self) pos)
((store! self newValue)
(operate-as cell store! self newValue)
(array-set! self pos newValue)
(set! pos (+ pos 1)))
((discard self value)
(set! most-recent-discard value))
((discarded-value self) most-recent-discard)
((print self port)
(format port "#<Cell-with-history ~s>" (fetch self))))))
(define-access-operation fetch)
(add-setter fetch store!)
(define foo (make-cell 1))
(print foo #f)
=> "#<Cell: 1>"
(set (fetch foo) 2)
=>
(print foo #f)
=> "#<Cell: 2>"
(fetch foo)
=> 2
(require 'logical)
The bit-twiddling functions are made available through the use of the
logical package. logical is loaded by inserting
(require 'logical) before the code that uses these
functions.
Example:
(number->string (logand #b1100 #b1010) 2) => "1000"
Example:
(number->string (logior #b1100 #b1010) 2) => "1110"
Example:
(number->string (logxor #b1100 #b1010) 2) => "110"
Example:
(number->string (lognot #b10000000) 2) => "-10000001" (number->string (lognot #b0) 2) => "-1"
(logtest j k) == (not (zero? (logand j k))) (logtest #b0100 #b1011) => #f (logtest #b0100 #b0111) => #t
(logbit? index j) == (logtest (integer-expt 2 index) j) (logbit? 0 #b1101) => #t (logbit? 1 #b1101) => #f (logbit? 2 #b1101) => #t (logbit? 3 #b1101) => #t (logbit? 4 #b1101) => #f
(inexact->exact (floor (* int (expt 2 count)))).
Example:
(number->string (ash #b1 3) 2) => "1000" (number->string (ash #b1010 -1) 2) => "101"
Example:
(logcount #b10101010) => 4 (logcount 0) => 0 (logcount -2) => 1
Example:
(integer-length #b10101010) => 8 (integer-length 0) => 0 (integer-length #b1111) => 4
Example:
(integer-expt 2 5) => 32 (integer-expt -3 3) => -27
Example:
(number->string (bit-extract #b1101101010 0 4) 2) => "1010" (number->string (bit-extract #b1101101010 4 9) 2) => "10110"
(require 'modular)
(d x y) such that d = gcd(n1,
n2) = n1 * x + n2 * y.
(quotient (+ -1 n) -2) for positive odd integer n.
modular: procedures.
(modulo n (modulus->integer
modulus)) in the representation specified by modulus.
The rest of these functions assume normalized arguments; That is, the arguments are constrained by the following table:
For all of these functions, if the first argument (modulus) is:
positive?
zero?
negative?
(+ 1 (* -2 modulus)), but with symmetric
representation; i.e. (<= (- modulus) n
modulus).
If all the arguments are fixnums the computation will use only fixnums.
#t if there exists an integer n such that k * n
== 1 mod modulus, and #f otherwise.
The Scheme code for modular:* with negative modulus is not
completed for fixnum-only implementations.
(require 'primes)
This package tests and generates prime numbers. The strategy used is as follows:
The Miller-Rabin test is a Monte-Carlo test--in other words, it's fast and it gets the right answer with high probability. For a candidate that is prime, the Miller-Rabin test is certain to report "prime"; it will never report "composite". However, for a candidate that is composite, there is a (small) probability that the Miller-Rabin test will erroneously report "prime". This probability can be made arbitarily small by adjusting the number of iterations of the Miller-Rabin test.
#t if candidate is probably prime. The optional
parameter iter controls the number of iterations of the
Miller-Rabin test. The probability of a composite candidate being
mistaken for a prime is at most (1/4)^iter. The default value of
iter is 15, which makes the probability less than 1 in 10^9.
count odd probable primes less (more)
than or equal to start. The optional parameter iter
controls the number of iterations of the Miller-Rabin test for each
candidate. The probability of a composite candidate being mistaken for
a prime is at most (1/4)^iter. The default value of iter
is 15, which makes the probability less than 1 in 10^9.
Rabin and Miller's result can be summarized as follows. Let p
(the candidate prime) be any odd integer greater than 2. Let b
(the "base") be an integer in the range 2 ... p-1. There is a
fairly simple Boolean function--call it C, for
"Composite"---with the following properties:
p is prime, C(p, b) is false for all b in the range
2 ... p-1.
p is composite, C(p, b) is false for at most 1/4 of all
b in the range 2 ... p-1. (If the test fails for base
b, p is called a strong pseudo-prime to base
b.)
For details of C, and why it fails for at most 1/4 of the
potential bases, please consult a book on number theory or cryptography
such as "A Course in Number Theory and Cryptography" by Neal Koblitz,
published by Springer-Verlag 1994.
There is nothing probablistic about this result. It's true for all
p. If we had time to test (1/4)p + 1 different bases, we
could definitively determine the primality of p. For large
candidates, that would take much too long--much longer than the simple
approach of dividing by all numbers up to sqrt(p). This is
where probability enters the picture.
Suppose we have some candidate prime p. Pick a random integer
b in the range 2 ... p-1. Compute C(p,b). If
p is prime, the result will certainly be false. If p is
composite, the probability is at most 1/4 that the result will be false
(demonstrating that p is a strong pseudoprime to base b).
The test can be repeated with other random bases. If p is prime,
each test is certain to return false. If p is composite, the
probability of C(p,b) returning false is at most 1/4 for each
test. Since the b are chosen at random, the tests outcomes are
independent. So if p is composite and the test is repeated, say,
15 times, the probability of it returning false all fifteen times is at
most (1/4)^15, or about 10^-9. If the test is repeated 30 times, the
probability of failure drops to at most 8.3e-25.
Rabin and Miller's result holds for all candidates p.
However, if the candidate p is picked at random, the probability
of the Miller-Rabin test failing is much less than the computed bound.
This is because, for most composite numbers, the fraction of
bases that cause the test to fail is much less than 1/4. For example,
if you pick a random odd number less than 1000 and apply the
Miller-Rabin test with only 3 random bases, the computed failure bound
is (1/4)^3, or about 1.6e-2. However, the actual probability of failure
is much less--about 7.2e-5. If you accidentally pick 703 to test for
primality, the probability of failure is (161/703)^3, or about 1.2e-2,
which is almost as high as the computed bound. This is because 703 is a
strong pseudoprime to 161 bases. But if you pick at random there is
only a small chance of picking 703, and no other number less than 1000
has that high a percentage of pseudoprime bases.
The Miller-Rabin test is sometimes used in a slightly different fashion, where it can, at least in principle, cause problems. The weaker version uses small prime bases instead of random bases. If you are picking candidates at random and testing for primality, this works well since very few composites are strong pseudo-primes to small prime bases. (For example, there is only one composite less than 2.5e10 that is a strong pseudo-prime to the bases 2, 3, 5, and 7.) The problem with this approach is that once a candidate has been picked, the test is deterministic. This distinction is subtle, but real. With the randomized test, for any candidate you pick--even if your candidate-picking procedure is strongly biased towards troublesome numbers, the test will work with high probability. With the deterministic version, for any particular candidate, the test will either work (with probability 1), or fail (with probability 1). It won't fail for very many candidates, but that won't be much consolation if your candidate-picking procedure is somehow biased toward troublesome numbers.
(require 'factor)
(sort! (factor k) <).Note: The rest of these procedures implement the Solovay-Strassen primality test. This test has been superseeded by the faster See section Prime Testing and Generation. However these are left here as they take up little space and may be of use to an implementation without bignums.
See Robert Solovay and Volker Strassen, A Fast Monte-Carlo Test for Primality, SIAM Journal on Computing, 1977, pp 84-85.
#f if p is composite; #t if p is
prime. There is a slight chance (expt 2 (- prime:trials)) that a
composite will return #t.
(require 'random)
The optional argument state must be of the type produced by
(make-random-state). It defaults to the value of the variable
*random-state*. This object is used to maintain the state of the
pseudo-random-number generator and is altered as a side effect of the
random operation.
random uses by default. The nature
of this data structure is implementation-dependent. It may be printed
out and successfully read back in, but may or may not function correctly
as a random-number state object in another implementation.
*random-state* and as a second argument to
random. If argument state is given, a copy of it is
returned. Otherwise a copy of *random-state* is returned.If inexact numbers are support by the Scheme implementation, `randinex.scm' will be loaded as well. `randinex.scm' contains procedures for generating inexact distributions.
(vector-length vect), the
coordinates are uniformly distributed within the unit n-shere.
The sum of the squares of the numbers is returned.
(vector-length vect), the coordinates are
uniformly distributed over the surface of the unit n-shere.
(+ m (* d
(random:normal))).
(require 'make-crc)
The integer degree, if given, specifies the degree of the polynomial being computed -- which is also the number of bits computed in the checksums. The default value is 32.
The integer generator specifies the polynomial being computed. The power of 2 generating each 1 bit is the exponent of a term of the polynomial. The bit at position degree is implicit and should not be part of generator. This allows systems with numbers limited to 32 bits to calculate 32 bit checksums. The default value of generator when degree is 32 (its default) is:
(make-port-crc 32 #b00000100110000010001110110110111)
Creates a procedure to calculate the P1003.2/D11.2 (POSIX.2) 32-bit checksum from the polynomial:
32 26 23 22 16 12 11
( x + x + x + x + x + x + x +
10 8 7 5 4 2 1
x + x + x + x + x + x + x + 1 ) mod 2
(require 'make-crc) (define crc32 (slib:eval (make-port-crc))) (define (file-check-sum file) (call-with-input-file file crc32)) (file-check-sum (in-vicinity (library-vicinity) "ratize.scm")) => 3553047446
(require 'charplot)
The plotting procedure is made available through the use of the
charplot package. charplot is loaded by inserting
(require 'charplot) before the code that uses this
procedure.
Example:
(require 'charplot)
(set! charplot:height 19)
(set! charplot:width 45)
(define (make-points n)
(if (zero? n)
'()
(cons (cons (/ n 6) (sin (/ n 6))) (make-points (1- n)))))
(plot! (make-points 37) "x" "Sin(x)")
-|
Sin(x) ______________________________________________
1.25|- |
| |
1|- **** |
| ** ** |
750.0e-3|- * * |
| * * |
500.0e-3|- * * |
| * |
250.0e-3|- * |
| * * |
0|-------------------*--------------------------|
| * |
-250.0e-3|- * * |
| * * |
-500.0e-3|- * |
| * * |
-750.0e-3|- * * |
| ** ** |
-1|- **** |
|____________:_____._____:_____._____:_________|
x 2 4
(require 'root)
#f if such an integer can't be found.
To find the closest integer to a given integers square root:
(define (integer-sqrt y) (newton:find-integer-root (lambda (x) (- (* x x) y)) (lambda (x) (* 2 x)) (ash 1 (quotient (integer-length y) 2)))) (integer-sqrt 15) => 4
abs(f(x)) is less than prec; or
returns #f if such a real can't be found.
If prec is instead a negative integer, newton:find-root
returns the result of -prec iterations.
H. J. Orchard, The Laguerre Method for Finding the Zeros of Polynomials, IEEE Transactions on Circuits and Systems, Vol. 36, No. 11, November 1989, pp 1377-1381.
There are 2 errors in Orchard's Table II. Line k=2 for starting value of 1000+j0 should have Z_k of 1.0475 + j4.1036 and line k=2 for starting value of 0+j1000 should have Z_k of 1.0988 + j4.0833.
magnitude(f(z)) is less than prec; or returns
#f if such a number can't be found.
If prec is instead a negative integer, laguerre:find-root
returns the result of -prec iterations.
magnitude(f(z)) is less than prec; or
returns #f if such a number can't be found.
If prec is instead a negative integer,
laguerre:find-polynomial-root returns the result of -prec
iterations.
Anything that doesn't fall neatly into any of the other categories winds up here.
(require 'batch)
The batch procedures provide a way to write and execute portable scripts
for a variety of operating systems. Each batch: procedure takes
as its first argument a parameter-list (see section Parameter lists). This
parameter-list argument parms contains named associations. Batch
currently uses 2 of these:
batch-port
batch-dialect
`batch.scm' uses 2 enhanced relational tables (see section Database Utilities) to store information linking the names of
operating-systems to batch-dialectes.
operating-system and batch-dialect tables and adds
the domain operating-system to the enhanced relational database
database.
batch:platform is set to (software-type)
(see section Configuration) unless (software-type) is unix,
in which case finer distinctions are made.
batch:call-with-output-script writes an appropriate
header to file and then calls proc with file as the
only argument. If file is a string,
batch:call-with-output-script opens a output-file of name
file, writes an appropriate header to file, and then calls
proc with the newly opened port as the only argument. Otherwise,
batch:call-with-output-script acts as if it was called with the
result of (current-output-port) as its third argument.
#t if successful, #f if not.
batch:apply-chop-to-fit calls proc with arg1,
arg2, ..., and chunk, where chunk is a subset of
list. batch:apply-chop-to-fit tries proc with
successively smaller subsets of list until either proc
returns non-false, or the chunks become empty.
The rest of the batch: procedures write (or execute if
batch-dialect is system) commands to the batch port which
has been added to parms or (copy-tree parms) by the
code:
(adjoin-parameters! parms (list 'batch-port port))
batch:try-system (below) with arguments, but signals an
error if batch:try-system returns #f.
These functions return a non-false value if the command was successfully
translated into the batch dialect and #f if not. In the case of
the system dialect, the value is non-false if the operation
suceeded.
batch-port in parms which executes
the program named string1 with arguments string2 ....
batch-port in parms which executes
the batch script named string1 with arguments string2
....
Note: batch:run-script and batch:try-system are not the
same for some operating systems (VMS).
batch-port in
parms.
batch-port in parms which create a
file named file with contents line1 ....
batch-port in parms which deletes
the file named file.
batch-port in parms which renames
the file old-name to new-name.
In addition, batch provides some small utilities very useful for writing scripts:
str but with the suffix string
old removed and the suffix string new appended. If the end
of str does not match old, an error is signaled.
equal? to elements of
list2, then those elements will appear first and in the order of
list1.
equal? to elements of
list1, then those elements will appear last and in the order of
list2.
batch-dialect to be used for the
operating-system named osname. os->batch-dialect uses the
tables added to database by batch:initialize!.
Here is an example of the use of most of batch's procedures:
(require 'database-utilities)
(require 'parameters)
(require 'batch)
(define batch (create-database #f 'alist-table))
(batch:initialize! batch)
(define my-parameters
(list (list 'batch-dialect (os->batch-dialect batch:platform))
(list 'platform batch:platform)
(list 'batch-port (current-output-port)))) ;gets filled in later
(batch:call-with-output-script
my-parameters
"my-batch"
(lambda (batch-port)
(adjoin-parameters! my-parameters (list 'batch-port batch-port))
(and
(batch:comment my-parameters
"================ Write file with C program.")
(batch:rename-file my-parameters "hello.c" "hello.c~")
(batch:lines->file my-parameters "hello.c"
"#include <stdio.h>"
"int main(int argc, char **argv)"
"{"
" printf(\"hello world\\n\");"
" return 0;"
"}" )
(batch:system my-parameters "cc" "-c" "hello.c")
(batch:system my-parameters "cc" "-o" "hello"
(replace-suffix "hello.c" ".c" ".o"))
(batch:system my-parameters "hello")
(batch:delete-file my-parameters "hello")
(batch:delete-file my-parameters "hello.c")
(batch:delete-file my-parameters "hello.o")
(batch:delete-file my-parameters "my-batch")
)))
Produces the file `my-batch':
#!/bin/sh
# "my-batch" build script created Sat Jun 10 21:20:37 1995
# ================ Write file with C program.
mv -f hello.c hello.c~
rm -f hello.c
echo '#include <stdio.h>'>>hello.c
echo 'int main(int argc, char **argv)'>>hello.c
echo '{'>>hello.c
echo ' printf("hello world\n");'>>hello.c
echo ' return 0;'>>hello.c
echo '}'>>hello.c
cc -c hello.c
cc -o hello hello.o
hello
rm -f hello
rm -f hello.c
rm -f hello.o
rm -f my-batch
When run, `my-batch' prints:
bash$ my-batch mv: hello.c: No such file or directory hello world
(require 'common-list-functions)
The procedures below follow the Common LISP equivalents apart from optional arguments in some cases.
make-list creates and returns a list of k elements. If
init is included, all elements in the list are initialized to
init.
Example:
(make-list 3) => (#<unspecified> #<unspecified> #<unspecified>) (make-list 5 'foo) => (foo foo foo foo foo)
list except that the cdr of the last pair is the last
argument unless there is only one argument, when the result is just that
argument. Sometimes called cons*. E.g.:
(list* 1) => 1 (list* 1 2 3) => (1 2 . 3) (list* 1 2 '(3 4)) => (1 2 3 4) (list* args '()) == (list args)
copy-list makes a copy of lst using new pairs and returns
it. Only the top level of the list is copied, i.e., pairs forming
elements of the copied list remain eq? to the corresponding
elements of the original; the copy is, however, not eq? to the
original, but is equal? to it.
Example:
(copy-list '(foo foo foo)) => (foo foo foo) (define q '(foo bar baz bang)) (define p q) (eq? p q) => #t (define r (copy-list q)) (eq? q r) => #f (equal? q r) => #t (define bar '(bar)) (eq? bar (car (copy-list (list bar 'foo)))) => #t @end lisp
eq? is used to test for membership by all the procedures below
which treat lists as sets.
adjoin returns the adjoint of the element e and the list
l. That is, if e is in l, adjoin returns
l, otherwise, it returns (cons e l).
Example:
(adjoin 'baz '(bar baz bang)) => (bar baz bang) (adjoin 'foo '(bar baz bang)) => (foo bar baz bang)
union returns the combination of l1 and l2.
Duplicates between l1 and l2 are culled. Duplicates within
l1 or within l2 may or may not be removed.
Example:
(union '(1 2 3 4) '(5 6 7 8)) => (4 3 2 1 5 6 7 8) (union '(1 2 3 4) '(3 4 5 6)) => (2 1 3 4 5 6)
intersection returns all elements that are in both l1 and
l2.
Example:
(intersection '(1 2 3 4) '(3 4 5 6)) => (3 4) (intersection '(1 2 3 4) '(5 6 7 8)) => ()
set-difference returns the union of all elements that are in
l1 but not in l2.
Example:
(set-difference '(1 2 3 4) '(3 4 5 6)) => (1 2) (set-difference '(1 2 3 4) '(1 2 3 4 5 6)) => ()
member-if returns lst if (pred element)
is #t for any element in lst. Returns #f if
pred does not apply to any element in lst.
Example:
(member-if vector? '(1 2 3 4)) => #f (member-if number? '(1 2 3 4)) => (1 2 3 4)
some i.e., lst plus any optional arguments.
pred is applied to successive elements of the list arguments in
order. some returns #t as soon as one of these
applications returns #t, and is #f if none returns
#t. All the lists should have the same length.
Example:
(some odd? '(1 2 3 4)) => #t (some odd? '(2 4 6 8)) => #f (some > '(2 3) '(1 4)) => #f
every is analogous to some except it returns #t if
every application of pred is #t and #f
otherwise.
Example:
(every even? '(1 2 3 4)) => #f (every even? '(2 4 6 8)) => #t (every > '(2 3) '(1 4)) => #f
notany is analogous to some but returns #t if no
application of pred returns #t or #f as soon as any
one does.
notevery is analogous to some but returns #t as soon
as an application of pred returns #f, and #f
otherwise.
Example:
(notevery even? '(1 2 3 4)) => #t (notevery even? '(2 4 6 8)) => #f
find-if searches for the first element in lst such
that (pred element) returns #t. If it finds
any such element in lst, element is returned.
Otherwise, #f is returned.
Example:
(find-if number? '(foo 1 bar 2)) => 1 (find-if number? '(foo bar baz bang)) => #f (find-if symbol? '(1 2 foo bar)) => foo
remove removes all occurrences of elt from lst using
eqv? to test for equality and returns everything that's left.
N.B.: other implementations (Chez, Scheme->C and T, at least) use
equal? as the equality test.
Example:
(remove 1 '(1 2 1 3 1 4 1 5)) => (2 3 4 5) (remove 'foo '(bar baz bang)) => (bar baz bang)
remove-if removes all elements from lst where
(pred element) is #t and returns everything
that's left.
Example:
(remove-if number? '(1 2 3 4)) => () (remove-if even? '(1 2 3 4 5 6 7 8)) => (1 3 5 7)
remove-if-not removes all elements from lst for which
(pred element) is #f and returns everything that's
left.
Example:
(remove-if-not number? '(foo bar baz)) => () (remove-if-not odd? '(1 2 3 4 5 6 7 8)) => (1 3 5 7)
#t if 2 members of lst are equal?, #f
otherwise.
Example:
(has-duplicates? '(1 2 3 4)) => #f (has-duplicates? '(2 4 3 4)) => #t
position returns the 0-based position of obj in lst,
or #f if obj does not occur in lst.
Example:
(position 'foo '(foo bar baz bang)) => 0 (position 'baz '(foo bar baz bang)) => 2 (position 'oops '(foo bar baz bang)) => #f
reduce combines all the elements of a sequence using a binary
operation (the combination is left-associative). For example, using
+, one can add up all the elements. reduce allows you to
apply a function which accepts only two arguments to more than 2
objects. Functional programmers usually refer to this as foldl.
collect:reduce (See section Collections) provides a version of
collect generalized to collections.
Example:
(reduce + '(1 2 3 4))
=> 10
(define (bad-sum . l) (reduce + l))
(bad-sum 1 2 3 4)
== (reduce + (1 2 3 4))
== (+ (+ (+ 1 2) 3) 4)
=> 10
(bad-sum)
== (reduce + ())
=> ()
(reduce string-append '("hello" "cruel" "world"))
== (string-append (string-append "hello" "cruel") "world")
=> "hellocruelworld"
(reduce anything '())
=> ()
(reduce anything '(x))
=> x
What follows is a rather non-standard implementation of reverse
in terms of reduce and a combinator elsewhere called
C.
;;; Contributed by Jussi Piitulainen (jpiitula@ling.helsinki.fi)
(define commute
(lambda (f)
(lambda (x y)
(f y x))))
(define reverse
(lambda (args)
(reduce-init (commute cons) args)))
reduce-init is the same as reduce, except that it implicitly
inserts init at the start of the list. reduce-init is
preferred if you want to handle the null list, the one-element, and
lists with two or more elements consistently. It is common to use the
operator's idempotent as the initializer. Functional programmers
usually call this foldl.
Example:
(define (sum . l) (reduce-init + 0 l))
(sum 1 2 3 4)
== (reduce-init + 0 (1 2 3 4))
== (+ (+ (+ (+ 0 1) 2) 3) 4)
=> 10
(sum)
== (reduce-init + 0 '())
=> 0
(reduce-init string-append "@" '("hello" "cruel" "world"))
==
(string-append (string-append (string-append "@" "hello")
"cruel")
"world")
=> "@hellocruelworld"
Given a differentiation of 2 arguments, diff, the following will
differentiate by any number of variables.
(define (diff* exp . vars) (reduce-init diff exp vars))
Example:
;;; Real-world example: Insertion sort using reduce-init.
(define (insert l item)
(if (null? l)
(list item)
(if (< (car l) item)
(cons (car l) (insert (cdr l) item))
(cons item l))))
(define (insertion-sort l) (reduce-init insert '() l))
(insertion-sort '(3 1 4 1 5)
== (reduce-init insert () (3 1 4 1 5))
== (insert (insert (insert (insert (insert () 3) 1) 4) 1) 5)
== (insert (insert (insert (insert (3)) 1) 4) 1) 5)
== (insert (insert (insert (1 3) 4) 1) 5)
== (insert (insert (1 3 4) 1) 5)
== (insert (1 1 3 4) 5)
=> (1 1 3 4 5)
@end lisp
butlast returns all but the last n elements of
lst.
Example:
(butlast '(1 2 3 4) 3) => (1) (butlast '(1 2 3 4) 4) => ()
nthcdr takes n cdrs of lst and returns the
result. Thus (nthcdr 3 lst) == (cdddr
lst)
Example:
(nthcdr 2 '(1 2 3 4)) => (3 4) (nthcdr 0 '(1 2 3 4)) => (1 2 3 4)
last returns the last n elements of lst. n
must be a non-negative integer.
Example:
(last '(foo bar baz bang) 2) => (baz bang) (last '(1 2 3) 0) => 0
These procedures may mutate the list they operate on, but any such mutation is undefined.
nconc destructively concatenates its arguments. (Compare this
with append, which copies arguments rather than destroying them.)
Sometimes called append! (See section Rev2 Procedures).
Example: You want to find the subsets of a set. Here's the obvious way:
(define (subsets set)
(if (null? set)
'(())
(append (mapcar (lambda (sub) (cons (car set) sub))
(subsets (cdr set)))
(subsets (cdr set)))))
But that does way more consing than you need. Instead, you could
replace the append with nconc, since you don't have any
need for all the intermediate results.
Example:
(define x '(a b c)) (define y '(d e f)) (nconc x y) => (a b c d e f) x => (a b c d e f)
nconc is the same as append! in `sc2.scm'.
nreverse reverses the order of elements in lst by mutating
cdrs of the list. Sometimes called reverse!.
Example:
(define foo '(a b c)) (nreverse foo) => (c b a) foo => (a)
Some people have been confused about how to use nreverse,
thinking that it doesn't return a value. It needs to be pointed out
that
(set! lst (nreverse lst))
is the proper usage, not
(nreverse lst)
The example should suffice to show why this is the case.
remove remove-if, and
remove-if-not.
Example:
(define lst '(foo bar baz bang)) (delete 'foo lst) => (bar baz bang) lst => (foo bar baz bang) (define lst '(1 2 3 4 5 6 7 8 9)) (delete-if odd? lst) => (2 4 6 8) lst => (1 2 4 6 8)
Some people have been confused about how to use delete,
delete-if, and delete-if, thinking that they dont' return
a value. It needs to be pointed out that
(set! lst (delete el lst))
is the proper usage, not
(delete el lst)
The examples should suffice to show why this is the case.
and? checks to see if all its arguments are true. If they are,
and? returns #t, otherwise, #f. (In contrast to
and, this is a function, so all arguments are always evaluated
and in an unspecified order.)
Example:
(and? 1 2 3) => #t (and #f 1 2) => #f
or? checks to see if any of its arguments are true. If any is
true, or? returns #t, and #f otherwise. (To
or as and? is to and.)
Example:
(or? 1 2 #f) => #t (or? #f #f #f) => #f
#t if object is not a pair and #f if it is
pair. (Called atom in Common LISP.)
(atom? 1) => #t (atom? '(1 2)) => #f (atom? #(1 2)) ; dubious! => #t
char, number,
string, symbol, list, or vector to
result-type (which must be one of these symbols).
(require 'format)
Returns #t, #f or a string; has side effect of printing
according to format-string. If destination is #t,
the output is to the current output port and #t is returned. If
destination is #f, a formatted string is returned as the
result of the call. NEW: If destination is a string,
destination is regarded as the format string; format-string is
then the first argument and the output is returned as a string. If
destination is a number, the output is to the current error port
if available by the implementation. Otherwise destination must be
an output port and #t is returned.
format-string must be a string. In case of a formatting error
format returns #f and prints a message on the current output or
error port. Characters are output as if the string were output by the
display function with the exception of those prefixed by a tilde
(~). For a detailed description of the format-string syntax
please consult a Common LISP format reference manual. For a test suite
to verify this format implementation load `formatst.scm'. Please
send bug reports to lutzeb@cs.tu-berlin.de.
Note: format is not reentrant, i.e. only one format-call
may be executed at a time.
Please consult a Common LISP format reference manual for a detailed description of the format string syntax. For a demonstration of the implemented directives see `formatst.scm'.
This implementation supports directive parameters and modifiers
(: and @ characters). Multiple parameters must be
separated by a comma (,). Parameters can be numerical parameters
(positive or negative), character parameters (prefixed by a quote
character ('), variable parameters (v), number of rest
arguments parameter (#), empty and default parameters. Directive
characters are case independent. The general form of a directive
is:
directive ::= ~{directive-parameter,}[:][@]directive-character
directive-parameter ::= [ [-|+]{0-9}+ | 'character | v | # ]
Documentation syntax: Uppercase characters represent the corresponding control directive characters. Lowercase characters represent control directive parameter descriptions.
~A
display does).
~@A
~mincol,colinc,minpad,padcharA
~S
write does).
~@S
~mincol,colinc,minpad,padcharS
~D
~@D
~:D
~mincol,padchar,commacharD
~X
~@X
~:X
~mincol,padchar,commacharX
~O
~@O
~:O
~mincol,padchar,commacharO
~B
~@B
~:B
~mincol,padchar,commacharB
~nR
~n,mincol,padchar,commacharR
~@R
~:R
~:@R
~P
~@P
y and ies.
~:P
~P but jumps 1 argument backward.
~:@P
~@P but jumps 1 argument backward.
~C
~@C
#\ prefixing).
~:C
^C for ASCII 03).
~F
~width,digits,scale,overflowchar,padcharF
~@F
~E
Eee).
~width,digits,exponentdigits,scale,overflowchar,padchar,exponentcharE
~@E
~G
~width,digits,exponentdigits,scale,overflowchar,padchar,exponentcharG
~@G
~$
~digits,scale,width,padchar$
~@$
~:@$
~:$
~%
~n%
~&
~n&
~& and then n-1 newlines.
~|
~n|
~~
~n~
~<newline>
~:<newline>
~@<newline>
~T
~@T
~colnum,colincT
~?
~@?
~(str~)
string-downcase).
~:(str~)
string-capitalize.
~@(str~)
string-capitalize-first.
~:@(str~)
string-upcase.
~*
~n*
~:*
~n:*
~@*
~n@*
~[str0~;str1~;...~;strn~]
~n[
~@[
~:[
~;
~:;
~{str~}
~n{
~:{
~@{
~:@{
~^
~n^
~n,m^
~n,m,k^
~:A
#f as an empty list (see below).
~:S
#f as an empty list (see below).
~<~>
~:^
~mincol,padchar,commachar,commawidthD
~mincol,padchar,commachar,commawidthX
~mincol,padchar,commachar,commawidthO
~mincol,padchar,commachar,commawidthB
~n,mincol,padchar,commachar,commawidthR
~I
~F~@Fi with passed parameters for
~F.
~Y
~K
~?.
~!
~_
#\space character
~n_
#\space characters.
~/
#\tab character
~n/
#\tab characters.
~nC
integer->char. n must be a positive decimal number.~:S
#<...> as strings "#<...>" so that the format output can always
be processed by read.
~:A
#<...> as strings "#<...>" so that the format output can always
be processed by read.
~Q
~:Q
~F, ~E, ~G, ~$
Format has some configuration variables at the beginning of `format.scm' to suit the systems and users needs. There should be no modification necessary for the configuration that comes with SLIB. If modification is desired the variable should be set after the format code is loaded. Format detects automatically if the running scheme system implements floating point numbers and complex numbers.
symbol->string so the case type of the
printed symbols is implementation dependent.
format:symbol-case-conv is a one arg closure which is either
#f (no conversion), string-upcase, string-downcase
or string-capitalize. (default #f)
#f)
~E printing. (default
#\E)
~A, ~S,
~P, ~X uppercase printing. SLIB format 1.4 uses C-style
printf padding support which is completely replaced by the CL
format padding style.
~, which is not documented
(ignores all characters inside the format string up to a newline
character). (7.1 implements ~a, ~s,
~newline, ~~, ~%, numerical and variable
parameters and :/@ modifiers in the CL sense).
~A and ~S which print in
uppercase. (Elk implements ~a, ~s, ~~, and
~% (no directive parameters or modifiers)).
~a, ~s, ~c, ~%, and ~~ (no directive
parameters or modifiers)).
This implementation of format is solely useful in the SLIB context because it requires other components provided by SLIB.
(require 'generic-write)
generic-write is a procedure that transforms a Scheme data value
(or Scheme program expression) into its textual representation and
prints it. The interface to the procedure is sufficiently general to
easily implement other useful formatting procedures such as pretty
printing, output to a string and truncated output.
#f to stop the transformation.
The value returned by generic-write is undefined.
Examples:
(write obj) == (generic-write obj #f #f display-string) (display obj) == (generic-write obj #t #f display-string)
where
display-string == (lambda (s) (for-each write-char (string->list s)) #t)
(require 'line-i/o)
current-input-port.
#f
is returned. port may be omitted, in which case it defaults to
the value returned by current-input-port.
current-input-port.
(require 'process)
process:queue. The
value returned is unspecified. The argument to proc should be
ignored. If proc returns, the process is killed.
process:queue and runs the next
process from process:queue. The value returned is
unspecified.
process:queue. If there are no more processes on
process:queue, (slib:exit) is called (See section System).
(require 'object->string)
(require 'pretty-print)
pretty-prints obj on port. If port is not
specified, current-output-port is used.
Example:
(pretty-print '((1 2 3 4 5) (6 7 8 9 10) (11 12 13 14 15)
(16 17 18 19 20) (21 22 23 24 25)))
-| ((1 2 3 4 5)
-| (6 7 8 9 10)
-| (11 12 13 14 15)
-| (16 17 18 19 20)
-| (21 22 23 24 25))
(require 'pprint-file)
(current-output-port).
outfile is a port or a string. If no outfile is specified
then current-output-port is assumed. These expanded expressions
are then pretty-printed to this port.
Whitepsace and comments (introduced by ;) which are not part of
scheme expressions are reproduced in the output. This procedure does
not affect the values returned by current-input-port and
current-output-port.
pprint-filter-file can be used to pre-compile macro-expansion and
thus can reduce loading time. The following will write into
`exp-code.scm' the result of expanding all defmacros in
`code.scm'.
(require 'pprint-file) (require 'defmacroexpand) (defmacro:load "my-macros.scm") (pprint-filter-file "code.scm" defmacro:expand* "exp-code.scm")
(require 'sort)
Many Scheme systems provide some kind of sorting functions. They do not, however, always provide the same sorting functions, and those that I have had the opportunity to test provided inefficient ones (a common blunder is to use quicksort which does not perform well).
Because sort and sort! are not in the standard, there is
very little agreement about what these functions look like. For
example, Dybvig says that Chez Scheme provides
(merge predicate list1 list2) (merge! predicate list1 list2) (sort predicate list) (sort! predicate list)
while MIT Scheme 7.1, following Common LISP, offers unstable
(sort list predicate)
TI PC Scheme offers
(sort! list/vector predicate?)
and Elk offers
(sort list/vector predicate?) (sort! list/vector predicate?)
Here is a comprehensive catalogue of the variations I have found.
sort and sort! may be provided.
sort may be provided without sort!.
sort! may be provided without sort.
<.
<=.
(sort predicate? sequence).
(sort sequence predicate?).
(sort sequence &optional (predicate? <)).
All of this variation really does not help anybody. A nice simple merge sort is both stable and fast (quite a lot faster than quick sort).
I am providing this source code with no restrictions at all on its use (but please retain D.H.D.Warren's credit for the original idea). You may have to rename some of these functions in order to use them in a system which already provides incompatible or inferior sorts. For each of the functions, only the top-level define needs to be edited to do that.
I could have given these functions names which would not clash with any Scheme that I know of, but I would like to encourage implementors to converge on a single interface, and this may serve as a hint. The argument order for all functions has been chosen to be as close to Common LISP as made sense, in order to avoid NIH-itis.
Each of the five functions has a required last parameter which is
a comparison function. A comparison function f is a function of
2 arguments which acts like <. For example,
(not (f x x)) (and (f x y) (f y z)) == (f x z)
The standard functions <, >, char<?, char>?,
char-ci<?, char-ci>?, string<?, string>?,
string-ci<?, and string-ci>? are suitable for use as
comparison functions. Think of (less? x y) as saying when
x must not precede y.
#t when the sequence argument is in non-decreasing order
according to less? (that is, there is no adjacent pair ... x
y ... for which (less? y x)).
Returns #f when the sequence contains at least one out-of-order
pair. It is an error if the sequence is neither a list nor a vector.
sort is our sort! (well,
in fact Common LISP's stable-sort is our sort!, merge sort
is fast as well as stable!) so adapting CL code to Scheme takes a
bit of work anyway. I did, however, appeal to CL to determine the
order of the arguments.
The code of merge and merge! could have been quite a bit
simpler, but they have been coded to reduce the amount of work done per
iteration. (For example, we only have one null? test per
iteration.)
(sorted? (sort sequence less?) less?). The original sequence is
not altered in any way. The new sequence shares its elements
with the old one; no elements are copied.
Some people have been confused about how to use sort!, thinking
that it doesn't return a value. It needs to be pointed out that
(set! slist (sort! slist <))
is the proper usage, not
(sort! slist <)
Note that these functions do not accept a CL-style `:key' argument. A simple device for obtaining the same expressiveness is to define
(define (keyed less? key) (lambda (x y) (less? (key x) (key y))))
and then, when you would have written
(sort a-sequence #'my-less :key #'my-key)
in Common LISP, just write
(sort! a-sequence (keyed my-less? my-key))
in Scheme.
(require 'topological-sort) or (require 'tsort)
The algorithm is inspired by Cormen, Leiserson and Rivest (1990) Introduction to Algorithms, chapter 23.
eq?, eqv?, equal?, =,
char=?, char-ci=?, string=?, or string-ci=?.
Sort the directed acyclic graph dag so that for every edge from vertex u to v, u will come before v in the resulting list of vertices.
Time complexity: O (|V| + |E|)
Example (from Cormen):
Prof. Bumstead topologically sorts his clothing when getting dressed. The first argument to `tsort' describes which garments he needs to put on before others. (For example, Prof Bumstead needs to put on his shirt before he puts on his tie or his belt.) `tsort' gives the correct order of dressing:
(require 'tsort)
(tsort '((shirt tie belt)
(tie jacket)
(belt jacket)
(watch)
(pants shoes belt)
(undershorts pants shoes)
(socks shoes))
eq?)
=>
(socks undershorts pants shoes watch shirt belt tie jacket)
(require 'stdio)
requires printf and scanf and additionally defines
the symbols:
(current-input-port).
(current-output-port).
(current-error-port).
(require 'printf)
Each function converts, formats, and outputs its arg1 ... arguments according to the control string format argument and returns the number of characters output.
printf sends its output to the port (current-output-port).
fprintf sends its output to the port port. sprintf
string-set!s locations of the non-constant string argument
str to the output characters.
Note: sprintf should be changed to a macro so a
substringexpression could be used for the str argument.
The string format contains plain characters which are copied to the output stream, and conversion specifications, each of which results in fetching zero or more of the arguments arg1 .... The results are undefined if there are an insufficient number of arguments for the format. If format is exhausted while some of the arg1 ... arguments remain unused, the excess arg1 ... arguments are ignored.
The conversion specifications in a format string have the form:
% [ flags ] [ width ] [ . precision ] [ type ] conversion
An output conversion specifications consist of an initial `%' character followed in sequence by:
scanf functions with the `%i' conversion (see section Standard Formatted Input).
6. If the precision is explicitly 0,
the decimal point character is suppressed.
For the `%g' and `%G' conversions, the precision specifies how
many significant digits to print. Significant digits are the first
digit before the decimal point, and all the digits after it. If the
precision is 0 or not specified for `%g' or `%G', it is
treated like a value of 1. If the value being printed cannot be
expressed accurately in the specified number of digits, the value is
rounded to the nearest number that fits.
For exact conversions, if a precision is supplied it specifies the
minimum number of digits to appear; leading zeros are produced if
necessary. If a precision is not supplied, the number is printed with
as many digits as necessary. Converting an exact `0' with an
explicit precision of zero produces no characters.
scanf
for input (see section Standard Formatted Input).
Note: Inexact conversions are not supported yet.
write (which can be read using read); otherwise,
output is as display prints. A precision specifies the maximum
number of characters to output; otherwise as many characters as needed
are output.
Note: `%a' and `%A' are SLIB extensions.
(require 'scanf)
Each function reads characters, interpreting them according to the control string format argument.
scanf-read-list returns a list of the items specified as far as
the input matches format. scanf, fscanf, and
sscanf return the number of items successfully matched and
stored. scanf, fscanf, and sscanf also set the
location corresponding to arg1 ... using the methods:
set!
set-car!
set-cdr!
vector-set!
substring-move-left!
The argument to a substring expression in arg1 ... must
be a non-constant string. Characters will be stored starting at the
position specified by the second argument to substring. The
number of characters stored will be limited by either the position
specified by the third argument to substring or the length of the
matched string, whichever is less.
The control string, format, contains conversion specifications and other characters used to direct interpretation of input sequences. The control string contains:
Unless the specification contains the `n' conversion character (described below), a conversion specification directs the conversion of the next input field. The result of a conversion specification is returned in the position of the corresponding argument points, unless `*' indicates assignment suppression. Assignment suppression provides a way to describe an input field to be skipped. An input field is defined as a string of characters; it extends to the next inappropriate character or until the field width, if specified, is exhausted.
Note: This specification of format strings differs from the ANSI C and POSIX specifications. In SLIB, white space before an input field is not skipped unless white space appears before the conversion specification in the format string. In order to write format strings which work identically with ANSI C and SLIB, prepend whitespace to all conversion specifications except `[' and `c'.
The conversion code indicates the interpretation of the input field; For a suppressed field, no value is returned. The following conversion codes are legal:
scanf. No input is consumed by %n.
scanf cannot read a null string.
The scanf functions terminate their conversions at end-of-file,
at the end of the control string, or when an input character conflicts
with the control string. In the latter case, the offending character is
left unread in the input stream.
(require 'string-case)
(require 'string-port)
(require 'string-search)
#f if the string does not contain a
character char.
substring? returns the index of the first
character of the first substring of string that is equal to
pattern; or #f if string does not contain
pattern.
(substring? "rat" "pirate") => 2 (substring? "rat" "outrage") => #f (substring? "" any-string) => 0
#f when the str isn't found.
find-string-from-port? reads the port strictly
sequentially, and does not perform any buffering. So
find-string-from-port? can be used even if the in-port is
open to a pipe or other communication channel.
Note: The Tektronix graphics support files need more work, and are not complete.
The Tektronix 4000 series graphics protocol gives the user a 1024 by 1024 square drawing area. The origin is in the lower left corner of the screen. Increasing y is up and increasing x is to the right.
The graphics control codes are sent over the current-output-port and can be mixed with regular text and ANSI or other terminal control sequences.
The graphics control codes are sent over the current-output-port and can be mixed with regular text and ANSI or other terminal control sequences.
(require 'tree)
These are operations that treat lists a representations of trees.
subst makes a copy of tree, substituting new for
every subtree or leaf of tree which is equal? to old
and returns a modified tree. The original tree is unchanged, but
may share parts with the result.
substq and substv are similar, but test against old
using eq? and eqv? respectively.
Examples:
(substq 'tempest 'hurricane '(shakespeare wrote (the hurricane)))
=> (shakespeare wrote (the tempest))
(substq 'foo '() '(shakespeare wrote (twelfth night)))
=> (shakespeare wrote (twelfth night . foo) . foo)
(subst '(a . cons) '(old . pair)
'((old . spice) ((old . shoes) old . pair) (old . pair)))
=> ((old . spice) ((old . shoes) a . cons) (a . cons))
eq? to the original ones -- only the leaves are.
Example:
(define bar '(bar)) (copy-tree (list bar 'foo)) => ((bar) foo) (eq? bar (car (copy-tree (list bar 'foo)))) => #f
(require 'with-file)
(require 'transcript)
read-char, read, write-char,
write, display, and newline.
(require 'rev2-procedures)
The procedures below were specified in the Revised^2 Report on
Scheme. N.B.: The symbols 1+ and -1+ are not
R4RS syntax. Scheme->C, for instance, barfs on this
module.
0 <= start1 <= end1 <= (string-length string1) 0 <= start2 <= end1 - start1 + start2 <= (string-length string2)
substring-move-left! and substring-move-right! store
characters of string1 beginning with index start1
(inclusive) and ending with index end1 (exclusive) into
string2 beginning with index start2 (inclusive).
substring-move-left! stores characters in time order of
increasing indices. substring-move-right! stores characters in
time order of increasing indeces.
(= 0 (string-length str))
nconc.
(require 'rev4-optional-procedures)
For the specification of these optional procedures, See section `Standard procedures' in Revised(4) Scheme.
(require 'mutliarg/and-)
For the specification of these optional forms, See section `Numerical operations' in Revised(4) Scheme. The two-arg:* forms are
only defined if the implementation does not support the many-argument
forms.
/.
-.
(require 'multiarg-apply)
For the specification of this optional form, See section `Control features' in Revised(4) Scheme.
apply. Only defined for
implementations which don't support the many-argument version.
(require 'rationalize)
The procedure rationalize is interesting because most programming languages do not provide anything analogous to it. For simplicity, we present an algorithm which computes the correct result for exact arguments (provided the implementation supports exact rational numbers of unlimited precision), and produces a reasonable answer for inexact arguments when inexact arithmetic is implemented using floating-point. We thank Alan Bawden for contributing this algorithm.
(require 'promise)
Change occurrences of (delay expression) to
(make-promise (lambda () expression)) and (define
force promise:force) to implement promises if your implementation
doesn't support them
(see section `Control features' in Revised(4) Scheme).
(require 'dynamic-wind)
This facility is a generalization of Common LISP unwind-protect,
designed to take into account the fact that continuations produced by
call-with-current-continuation may be reentered.
dynamic-wind calls thunk1, thunk2, and then
thunk3. The value returned by thunk2 is returned as the
result of dynamic-wind. thunk3 is also called just before
control leaves the dynamic context of thunk2 by calling a
continuation created outside that context. Furthermore, thunk1 is
called before reentering the dynamic context of thunk2 by calling
a continuation created inside that context. (Control is inside the
context of thunk2 if thunk2 is on the current return stack).
Warning: There is no provision for dealing with errors or
interrupts. If an error or interrupt occurs while using
dynamic-wind, the dynamic environment will be that in effect at
the time of the error or interrupt.
(require 'values)
values takes any number of arguments, and passes (returns) them
to its continuation.
call-with-values calls thunk with a
continuation that, when passed some values, calls proc with those
values as arguments.
Except for continuations created by the call-with-values
procedure, all continuations take exactly one value, as now; the effect
of passing no value or more than one value to continuations that were
not created by the call-with-values procedure is
unspecified.
The procedures current-time, difftime, and
offset-time are supported by all implementations (SLIB provides
them if feature ('current-time) is missing. current-time
returns a calendar time (caltime) which can be a number or other
type.
get-universal-time in section CLTime. On implementations
which cannot support actual times, current-time will increment a
counter and return its value when called.
(+ caltime offset).
(require 'posix-time)
These procedures are intended to be compatible with Posix time conversion functions.
*timezone* is initialized by tzset.
localtime sets the variable
*timezone* with the difference between Coordinated Universal Time
(UTC) and local standard time in seconds by calling tzset.
The elements of the returned vector are as follows:
decode-universal-time.
"Wed Jun 30 21:49:08 1993".
(time:asctime (time:localtime caltime)).
(decode-universal-time (get-universal-time)).
current-time.
gmtime and localtime.
Notice that the values returned by decode-universal-time do not
match the arguments to encode-universal-time.
Notice that the values returned by decode-universal-time do not
match the arguments to encode-universal-time.
(require 'repl)
Here is a read-eval-print-loop which, given an eval, evaluates forms.
reads, repl:evals and writes expressions from
(current-input-port) to (current-output-port) until an
end-of-file is encountered. load, slib:eval,
slib:error, and repl:quit dynamically bound during
repl:top-level.
repl:top-level.
The repl: procedures establish, as much as is possible to do
portably, a top level environment supporting macros.
repl:top-level uses dynamic-wind to catch error conditions
and interrupts. If your implementation supports this you are all set.
Otherwise, if there is some way your implementation can catch error
conditions and interrupts, then have them call slib:error. It
will display its arguments and reenter repl:top-level.
slib:error dynamically bound by repl:top-level.
To have your top level loop always use macros, add any interrupt catching lines and the following lines to your Scheme init file:
(require 'macro) (require 'repl) (repl:top-level macro:eval)
(require 'qp)
When displaying error messages and warnings, it is paramount that the output generated for circular lists and large data structures be limited. This section supplies a procedure to do this. It could be much improved.
Notice that the neccessity for truncating output eliminates Common-Lisp's See section Format from consideration; even when variables
*print-level*and*print-level*are set, huge strings and bit-vectors are not limited.
qp writes its arguments, separated by spaces, to
(current-output-port). qp compresses printing by
substituting `...' for substructure it does not have sufficient
room to print. qpn is like qp but outputs a newline
before returning. qpr is like qpn except that it returns
its last argument.
*qp-width* is the largest number of characters that qp
should use.
(require 'debug)
Requiring debug automatically requires trace and
break.
An application with its own datatypes may want to substitute its own
printer for qp. This example shows how to do this:
(define qpn (lambda args) ...) (provide 'qp) (require 'debug)
defined at top-level in
file `file'.
defined at
top-level in file `file'.
(require 'break)
break or
abort, a message will appear when you (require 'break) or
(require 'debug) telling you to type (init-debug). This
is in order to establish a top-level continuation. Typing
(init-debug) at top level sets up a continuation for
break.
breakpoint is called before calling proc1 ....
The following routines are the procedures which actually do the tracing when this module is supplied by SLIB, rather than natively. If defmacros are not natively supported by your implementation, these might be more convenient to use.
(set! symbol (breakf symbol))
or
(set! symbol (breakf symbol 'symbol))
or
(define symbol (breakf function))
or
(define symbol (breakf function 'symbol))
(set! symbol (unbreakf symbol))
(require 'trace)
The following routines are the procedures which actually do the tracing when this module is supplied by SLIB, rather than natively. If defmacros are not natively supported by your implementation, these might be more convenient to use.
(set! symbol (tracef symbol))
or
(set! symbol (tracef symbol 'symbol))
or
(define symbol (tracef function))
or
(define symbol (tracef function 'symbol))
(set! symbol (untracef symbol))
(require 'getopt)
This routine implements Posix command line argument parsing. Notice
that returning values through global variables means that getopt
is not reentrant.
(vector-ref argv *optind*)) that matches a letter in
optstring. argv is a vector or list of strings, the 0th of
which getopt usually ignores. argc is the argument count, usually
the length of argv. optstring is a string of recognized
option characters; if a character is followed by a colon, the option
takes an argument which may be immediately following it in the string or
in the next element of argv.
*optind* is the index of the next element of the argv vector
to be processed. It is initialized to 1 by `getopt.scm', and
getopt updates it when it finishes with each element of
argv.
getopt returns the next option character from argv that
matches a character in optstring, if there is one that matches.
If the option takes an argument, getopt sets the variable
*optarg* to the option-argument as follows:
getopt returns an error
indication.
If, when getopt is called, the string (vector-ref argv
*optind*) either does not begin with the character #\- or is
just "-", getopt returns #f without changing
*optind*. If (vector-ref argv *optind*) is the string
"--", getopt returns #f after incrementing
*optind*.
If getopt encounters an option character that is not contained in
optstring, it returns the question-mark #\? character. If
it detects a missing option argument, it returns the colon character
#\: if the first character of optstring was a colon, or a
question-mark character otherwise. In either case, getopt sets
the variable getopt:opt to the option character that caused the
error.
The special option "--" can be used to delimit the end of the
options; #f is returned, and "--" is skipped.
RETURN VALUE
getopt returns the next option character specified on the command
line. A colon #\: is returned if getopt detects a missing argument
and the first character of optstring was a colon #\:.
A question-mark #\? is returned if getopt encounters an option
character not in optstring or detects a missing argument and the first
character of optstring was not a colon #\:.
Otherwise, getopt returns #f when all command line options have been
parsed.
Example:
#! /usr/local/bin/scm
;;;This code is SCM specific.
(define argv (program-arguments))
(require 'getopt)
(define opts ":a:b:cd")
(let loop ((opt (getopt (length argv) argv opts)))
(case opt
((#\a) (print "option a: " *optarg*))
((#\b) (print "option b: " *optarg*))
((#\c) (print "option c"))
((#\d) (print "option d"))
((#\?) (print "error" getopt:opt))
((#\:) (print "missing arg" getopt:opt))
((#f) (if (< *optind* (length argv))
(print "argv[" *optind* "]="
(list-ref argv *optind*)))
(set! *optind* (+ *optind* 1))))
(if (< *optind* (length argv))
(loop (getopt (length argv) argv opts))))
(slib:exit)
getopt-- is an extended version of getopt
which parses long option names of the form
`--hold-the-onions' and `--verbosity-level=extreme'.
Getopt-- behaves as getopt except for non-empty
options beginning with `--'.
Options beginning with `--' are returned as strings rather than
characters. If a value is assigned (using `=') to a long option,
*optarg* is set to the value. The `=' and value are
not returned as part of the option string.
No information is passed to getopt-- concerning which long
options should be accepted or whether such options can take arguments.
If a long option did not have an argument, *optarg will be set to
#f. The caller is responsible for detecting and reporting
errors.
(define opts ":-:b:")
(define argc 5)
(define argv '("foo" "-b9" "--f1" "--2=" "--g3=35234.342" "--"))
(define *optind* 1)
(define *optarg* #f)
(require 'qp)
(do ((i 5 (+ -1 i)))
((zero? i))
(define opt (getopt-- argc argv opts))
(print *optind* opt *optarg*)))
-|
2 #\b "9"
3 "f1" #f
4 "2" ""
5 "g3" "35234.342"
5 #f "35234.342"
(require 'read-command)
read-command converts a command line into a list of strings
suitable for parsing by getopt. The syntax of command lines
supported resembles that of popular shells. read-command
updates port to point to the first character past the command
delimiter.
If an end of file is encountered in the input before any characters are found that can begin an object or comment, then an end of file object is returned.
The port argument may be omitted, in which case it defaults to the
value returned by current-input-port.
The fields into which the command line is split are delimited by
whitespace as defined by char-whitespace?. The end of a command
is delimited by end-of-file or unescaped semicolon (;) or
newline. Any character can be literally included in a field by
escaping it with a backslach (\).
The initial character and types of fields recognized are:
read starting with this character. The
read expression is evaluated, converted to a string
(using display), and replaces the expression in the returned
field.
The comment field differs from the previous fields in that it must be
the first character of a command or appear after whitespace in order to
be recognized. # can be part of fields if these conditions are
not met. For instance, ab#c is just the field ab#c.
read-dommand-line and backslashes before newlines in
comments are also ignored.
If (provided? 'getenv):
#f is returned.
If (provided? 'system):
These variables and procedures are provided by all implementations.
source, or compiled. The cdr of the pathname
should be either a string or a list.
In the following three functions if feature is not a symbol it is assumed to be a pathname.
#t if feature is a member of *features* or
*modules* or if feature is supported by a file already
loaded and #f otherwise.
(not (provided? feature)) it is loaded if feature
is a pathname or if (assq feature *catalog*). Otherwise an
error is signaled.
*features* if
feature is a symbol and *modules* otherwise.
#t if feature is a member of *features* or
*modules* or if feature is supported by a file already
loaded. Returns a path if one was found in *catalog* under the
feature name, and #f otherwise. The path can either be a string
suitable as an argument to load or a pair as described above for
*catalog*.
Below is a list of features that are automatically determined by
require. For each item, (provided? 'feature) will
return #t if that feature is available, and #f if
not.
A vicinity is a descriptor for a place in the file system. Vicinities hide from the programmer the concepts of host, volume, directory, and version. Vicinities express only the concept of a file environment where a file name can be resolved to a file in a system independent manner. Vicinities can even be used on flat file systems (which have no directory structure) by having the vicinity express constraints on the file name. On most systems a vicinity would be a string. All of these procedures are file system dependent.
These procedures are provided by all implementations.
in-vicinity.
program-vicinity can
return incorrectl values if your program escapes back into a
load.
slib:load,
slib:load-source, slib:load-compiled,
open-input-file, open-output-file, etc. The returned
filename is filename in vicinity. in-vicinity should
allow filename to override vicinity when filename is
an absolute pathname and vicinity is equal to the value of
(user-vicinity). The behavior of in-vicinity when
filename is absolute and vicinity is not equal to the value
of (user-vicinity) is unspecified. For most systems
in-vicinity can be string-append.
sub-vicinity will
return a pathname of the subdirectory name of
vicinity.These constants and procedures describe characteristics of the Scheme and underlying operating system. They are provided by all implementations.
char->integer.
unix, vms, macos, amiga, or
ms-dos.
(slib:report-version) => slib "2a3" on scm "4e1" on unix
(slib:report-version) followed by
almost all the information neccessary for submitting a problem report.
An unspecified value is returned.
(slib:report)
=>
slib "2a3" on scm "4e1" on unix
(implementation-vicinity) is "/usr/local/src/scm/"
(library-vicinity) is "/usr/local/lib/slib/"
(scheme-file-suffix) is ".scm"
implementation *features* :
bignum complex real rational
inexact vicinity ed getenv
tmpnam system abort transcript
with-file ieee-p1178 rev4-report rev4-optional-procedures
hash object-hash delay eval
dynamic-wind multiarg-apply multiarg/and- logical
defmacro string-port source array-for-each
array full-continuation char-ready? line-i/o
i/o-extensions pipe
implementation *catalog* :
(rev4-optional-procedures . "/usr/local/lib/slib/sc4opt")
...
These procedures are provided by all implementations.
#t if the specified file exists. Otherwise, returns
#f. If the underlying implementation does not support this
feature then #f is always returned.
#f is returned. Otherwise, #t is
returned.
(tmpnam) will return different
pathnames.
(current-output-port).
Returns the width of port, which defaults to
(current-output-port) if absent. If the width cannot be
determined 79 is returned.
Returns the height of port, which defaults to
(current-output-port) if absent. If the height cannot be
determined 24 is returned.
Example:
(identity 3) => 3 (identity '(foo bar)) => (foo bar) (map identity lst) == (copy-list lst)
These were present in Scheme until R4RS (see section `Language changes' in Revised(4) Scheme).
#t.
#f.
(last-pair (cons 1 2))
=> (1 . 2)
(last-pair '(1 2))
=> (2)
== (cons 2 '())
These procedures are provided by all implementations.
(slib:load-source "foo") will
load from file `foo.scm'.
If an implementation does not support compiled code then
slib:load will be identical to slib:load-source.
eval returns the value of obj evaluated in the current top
level environment.
slib:eval-load procedure does not affect the values returned by
current-input-port and current-output-port.
#t, a success status is returned to the
system (if possible). If n is #f a failure is returned to
the system (if possible). If n is an integer, then n is
returned to the system (if possible). If the Scheme session cannot exit
an unspecified value is returned from slib:exit.
Several Scheme packages have been written using SLIB. There are several reasons why a package might not be included in the SLIB distribution:
Once an optional package is installed (and an entry added to
*catalog*, the require mechanism allows it to be called up
and used as easily as any other SLIB package. Some optional packages
(for which *catalog* already has entries) available from SLIB
sites are:
ftp-swiss.ai.mit.edu:pub/scm/slib-psd1-3.tar.gz prep.ai.mit.edu:pub/gnu/jacal/slib-psd1-3.tar.gz ftp.maths.tcd.ie:pub/bosullvn/jacal/slib-psd1-3.tar.gz ftp.cs.indiana.edu:/pub/scheme-repository/utl/slib-psd1-3.tar.gzWith PSD, you can run a Scheme program in an Emacs buffer, set breakpoints, single step evaluation and access and modify the program's variables. It works by instrumenting the original source code, so it should run with any R4RS compliant Scheme. It has been tested with SCM, Elk 1.5, and the sci interpreter in the Scheme->C system, but should work with other Schemes with a minimal amount of porting, if at all. Includes documentation and user's manual. Written by Pertti Kellom\"aki, pk@cs.tut.fi. The Lisp Pointers article describing PSD (Lisp Pointers VI(1):15-23, January-March 1993) is available as
http://www.cs.tut.fi/staff/pk/scheme/psd/article/article.html
ftp-swiss.ai.mit.edu:pub/scm/slib-schelog.tar.gz prep.ai.mit.edu:pub/gnu/jacal/slib-schelog.tar.gz ftp.maths.tcd.ie:pub/bosullvn/jacal/slib-schelog.tar.gz ftp.cs.indiana.edu:/pub/scheme-repository/utl/slib-schelog.tar.gz
This is an alphabetical list of all the procedures and macros in SLIB.
This is an alphabetical list of all the global variables in SLIB.
This document was generated on 17 December 1996 using the texi2html translator version 1.51.