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* NEWS: Added entry for optargs module.

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* ice-9/optargs.scm: New file.
* ice-9/Makefile.am (ice9_sources): Add optargs.scm here. Makefile.in
not regenerated because I don't have the right version of Automake.
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Maciej Stachowiak 1999-02-09 19:49:24 +00:00
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4
ChangeLog
View file

@ -1,3 +1,7 @@
1999-02-09 Maciej Stachowiak <mstachow@alum.mit.edu>
* NEWS: Added entry for optargs module.
1999-02-06 Jim Blandy <jimb@zwingli.cygnus.com>
* configure: Regenerated using autoconf 2.12.

76
NEWS
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@ -50,6 +50,82 @@ in backtraces.
* Changes to Scheme functions and syntax
** New syntax: lambda*
** New syntax: define*
** New syntax: define*-public
** New syntax: defmacro*
** New syntax: defmacro*-public
Guile now supports optional arguments.
`lambda*', `define*', `define*-public', `defmacro*' and
`defmacro*-public' are identical to the non-* versions except that
they use an extended type of parameter list that has the following BNF
syntax (parentheses are literal, square brackets indicate grouping,
and `*', `+' and `?' have the usual meaning):
ext-param-list ::= ( [identifier]* [#&optional [ext-var-decl]+]?
[#&key [ext-var-decl]+ [#&allow-other-keys]?]?
[[#&rest identifier]|[. identifier]]? ) | [identifier]
ext-var-decl ::= identifier | ( identifier expression )
The semantics are best illustrated with the following documentation
and examples for `lambda*':
lambda* args . body
lambda extended for optional and keyword arguments
lambda* creates a procedure that takes optional arguments. These
are specified by putting them inside brackets at the end of the
paramater list, but before any dotted rest argument. For example,
(lambda* (a b #&optional c d . e) '())
creates a procedure with fixed arguments a and b, optional arguments c
and d, and rest argument e. If the optional arguments are omitted
in a call, the variables for them are unbound in the procedure. This
can be checked with the bound? macro.
lambda* can also take keyword arguments. For example, a procedure
defined like this:
(lambda* (#&key xyzzy larch) '())
can be called with any of the argument lists (#:xyzzy 11)
(#:larch 13) (#:larch 42 #:xyzzy 19) (). Whichever arguments
are given as keywords are bound to values.
Optional and keyword arguments can also be given default values
which they take on when they are not present in a call, by giving a
two-item list in place of an optional argument, for example in:
(lambda* (foo #&optional (bar 42) #&key (baz 73)) (list foo bar baz))
foo is a fixed argument, bar is an optional argument with default
value 42, and baz is a keyword argument with default value 73.
Default value expressions are not evaluated unless they are needed
and until the procedure is called.
lambda* now supports two more special parameter list keywords.
lambda*-defined procedures now throw an error by default if a
keyword other than one of those specified is found in the actual
passed arguments. However, specifying #&allow-other-keys
immediately after the kyword argument declarations restores the
previous behavior of ignoring unknown keywords. lambda* also now
guarantees that if the same keyword is passed more than once, the
last one passed is the one that takes effect. For example,
((lambda* (#&key (heads 0) (tails 0)) (display (list heads tails)))
#:heads 37 #:tails 42 #:heads 99)
would result in (99 47) being displayed.
#&rest is also now provided as a synonym for the dotted syntax rest
argument. The argument lists (a . b) and (a #&rest b) are equivalent in
all respects to lambda*. This is provided for more similarity to DSSSL,
MIT-Scheme and Kawa among others, as well as for refugees from other
Lisp dialects.
Further documentation may be found in the optargs.scm file itself.
The optional argument module also exports the macros `let-optional',
`let-optional*', `let-keywords', `let-keywords*' and `bound?'. These
are not documented here because they may be removed in the future, but
full documentation is still available in optargs.scm.
** New syntax: and-let*
Guile now supports the `and-let*' form, described in the draft SRFI-2.

6
ice-9/ChangeLog
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@ -1,3 +1,9 @@
1999-02-09 Maciej Stachowiak <mstachow@alum.mit.edu>
* optargs.scm: New file.
* Makefile.am (ice9_sources): Add optargs.scm here. Makefile.in
not regenerated because I don't have the right version of Automake.
1999-02-06 Jim Blandy <jimb@zwingli.cygnus.com>
* and-let*.scm: New file, from Michael Livshin.

458
ice-9/optargs.scm Normal file
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@ -0,0 +1,458 @@
;;;; optargs.scm -- support for optional arguments
;;;;
;;;; Copyright (C) 1997, 1998, 1999 Free Software Foundation, Inc.
;;;;
;;;; This program is free software; you can redistribute it and/or modify
;;;; it under the terms of the GNU General Public License as published by
;;;; the Free Software Foundation; either version 2, or (at your option)
;;;; any later version.
;;;;
;;;; This program is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;;; GNU General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU General Public License
;;;; along with this software; see the file COPYING. If not, write to
;;;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
;;;;
;;;; Contributed by Maciej Stachowiak <mstachow@alum.mit.edu>
(define-module (ice-9 optargs))
;;; {Optional Arguments}
;;;
;;; The C interface for creating Guile procedures has a very handy
;;; "optional argument" feature. This module attempts to provide
;;; similar functionality for procedures defined in Scheme with
;;; a convenient and attractive syntax.
;;;
;;; exported macros are:
;;; bound?
;;; let-optional
;;; let-optional*
;;; let-keywords
;;; let-keywords*
;;; lambda*
;;; define*
;;; define*-public
;;; defmacro*
;;; defmacro*-public
;;;
;;;
;;; Summary of the lambda* extended parameter list syntax (brackets
;;; are used to indicate grouping only):
;;;
;;; ext-param-list ::= [identifier]* [#&optional [ext-var-decl]+]?
;;; [#&key [ext-var-decl]+ [#&allow-other-keys]?]?
;;; [[#&rest identifier]|[. identifier]]?
;;;
;;; ext-var-decl ::= identifier | ( identifier expression )
;;;
;;; The characters `*', `+' and `?' are not to be taken literally; they
;;; mean respectively, zero or more occurences, one or more occurences,
;;; and one or zero occurences.
;;;
;; bound? var
;; Checks if a variable is bound in the current environment.
;;
;; defined? doesn't quite cut it as it stands, since it only
;; cheks bindings in the top-level environment, not those in
;; local scope only.
;;
(defmacro-public bound? (var)
`(catch 'misc-error
(lambda ()
,var
(not (eq? ,var ,(variable-ref
(make-undefined-variable)))))
(lambda args #f)))
;; let-optional rest-arg (binding ...) . body
;; let-optional* rest-arg (binding ...) . body
;; macros used to bind optional arguments
;;
;; These two macros give you an optional argument interface that
;; is very "Schemey" and introduces no fancy syntax. They are
;; compatible with the scsh macros of the same name, but are slightly
;; extended. Each of binding may be of one of the forms <var> or
;; (<var> <default-value>). rest-arg should be the rest-argument of
;; the procedures these are used from. The items in rest-arg are
;; sequentially bound to the variable namess are given. When rest-arg
;; runs out, the remaining vars are bound either to the default values
;; or left unbound if no default value was specified. rest-arg remains
;; bound to whatever may have been left of rest-arg.
;;
(defmacro-public let-optional (REST-ARG BINDINGS . BODY)
(let-optional-template REST-ARG BINDINGS BODY 'let))
(defmacro-public let-optional* (REST-ARG BINDINGS . BODY)
(let-optional-template REST-ARG BINDINGS BODY 'let*))
;; let-keywords rest-arg allow-other-keys? (binding ...) . body
;; let-keywords* rest-arg allow-other-keys? (binding ...) . body
;; macros used to bind keyword arguments
;;
;; These macros pick out keyword arguments from rest-arg, but do not
;; modify it. This is consistent at least with Common Lisp, which
;; duplicates keyword args in the rest arg. More explanation of what
;; keyword arguments in a lambda list look like can be found below in
;; the documentation for lambda*. Bindings can have the same form as
;; for let-optional. If allow-other-keys? is false, an error will be
;; thrown if anything that looks like a keyword argument but does not
;; match a known keyword parameter will result in an error.
;;
(defmacro-public let-keywords (REST-ARG ALLOW-OTHER-KEYS? BINDINGS . BODY)
(let-keywords-template REST-ARG ALLOW-OTHER-KEYS? BINDINGS BODY 'let))
(defmacro-public let-keywords* (REST-ARG ALLOW-OTHER-KEYS? BINDINGS . BODY)
(let-keywords-template REST-ARG ALLOW-OTHER-KEYS? BINDINGS BODY 'let*))
;; some utility procedures for implementing the various let-forms.
(define (let-o-k-template REST-ARG BINDINGS BODY let-type proc)
(let ((bindings (map (lambda (x)
(if (list? x)
x
(list x (variable-ref
(make-undefined-variable)))))
BINDINGS)))
`(,let-type ,(map proc bindings) ,@BODY)))
(define (let-optional-template REST-ARG BINDINGS BODY let-type)
(if (null? BINDINGS)
`(begin ,@BODY)
(let-o-k-template REST-ARG BINDINGS BODY let-type
(lambda (optional)
`(,(car optional)
(cond
((not (null? ,REST-ARG))
(let ((result (car ,REST-ARG)))
,(list 'set! REST-ARG
`(cdr ,REST-ARG))
result))
(else
,(cadr optional))))))))
(define (let-keywords-template REST-ARG ALLOW-OTHER-KEYS? BINDINGS BODY let-type)
(if (null? BINDINGS)
`(begin ,@BODY)
(let* ((kb-list-gensym (gensym "kb:G"))
(bindfilter (lambda (key)
`(,(car key)
(cond
((assq ',(car key) ,kb-list-gensym)
=> cdr)
(else
,(cadr key)))))))
`(let* ((ra->kbl ,rest-arg->keyword-binding-list)
(,kb-list-gensym (ra->kbl ,REST-ARG ',(map
(lambda (x) (symbol->keyword (if (pair? x) (car x) x)))
BINDINGS)
,ALLOW-OTHER-KEYS?)))
,(let-o-k-template REST-ARG BINDINGS BODY let-type bindfilter)))))
(define (rest-arg->keyword-binding-list rest-arg keywords allow-other-keys?)
(if (null? rest-arg)
()
(let loop ((first (car rest-arg))
(rest (cdr rest-arg))
(accum ()))
(let ((next (lambda (a)
(if (null? (cdr rest))
a
(loop (cadr rest) (cddr rest) a)))))
(if (keyword? first)
(cond
((memq first keywords)
(if (null? rest)
(error "Keyword argument has no value.")
(next (cons (cons (keyword->symbol first)
(car rest)) accum))))
((not allow-other-keys?)
(error "Unknown keyword in arguments."))
(else (if (null? rest)
accum
(next accum))))
(if (null? rest)
accum
(loop (car rest) (cdr rest) accum)))))))
;; reader extensions for #&optional #&key #&allow-other-keys #&rest
;; These need to be quoted in normal code, but need not be in
;; an extended lambda-list provided by lambda*, define*, or
;; define*-public (see below). In other words, they act sort of like
;; symbols, except they aren't. They're being temporarily used until
;; #!optional and #!key and such are available. #&rest is provided for
;; the convenience of confused Common Lisp users, even though `.' will
;; do just as well.
(define the-optional-value
((record-constructor (make-record-type
'optional '() (lambda (o p)
(display "#&optional"))))))
(define the-key-value
((record-constructor (make-record-type
'key '() (lambda (o p)
(display "#&key"))))))
(define the-rest-value
((record-constructor (make-record-type
'rest '() (lambda (o p)
(display "#&rest" p))))))
(define the-allow-other-keys-value
((record-constructor (make-record-type
'allow-other-keys '() (lambda (o p)
(display "#&allow-other-keys" p))))))
(read-hash-extend #\& (lambda (c port)
(case (read port)
((optional) the-optional-value)
((key) the-key-value)
((rest) the-rest-value)
((allow-other-keys) the-allow-other-keys-value)
(else (error "Bad #& value.")))))
;; lambda* args . body
;; lambda extended for optional and keyword arguments
;;
;; lambda* creates a procedure that takes optional arguments. These
;; are specified by putting them inside brackets at the end of the
;; paramater list, but before any dotted rest argument. For example,
;; (lambda* (a b #&optional c d . e) '())
;; creates a procedure with fixed arguments a and b, optional arguments c
;; and d, and rest argument e. If the optional arguments are omitted
;; in a call, the variables for them are unbound in the procedure. This
;; can be checked with the bound? macro.
;;
;; lambda* can also take keyword arguments. For example, a procedure
;; defined like this:
;; (lambda* (#&key xyzzy larch) '())
;; can be called with any of the argument lists (#:xyzzy 11)
;; (#:larch 13) (#:larch 42 #:xyzzy 19) (). Whichever arguments
;; are given as keywords are bound to values.
;;
;; Optional and keyword arguments can also be given default values
;; which they take on when they are not present in a call, by giving a
;; two-item list in place of an optional argument, for example in:
;; (lambda* (foo #&optional (bar 42) #&key (baz 73)) (list foo bar baz))
;; foo is a fixed argument, bar is an optional argument with default
;; value 42, and baz is a keyword argument with default value 73.
;; Default value expressions are not evaluated unless they are needed
;; and until the procedure is called.
;;
;; lambda* now supports two more special parameter list keywords.
;;
;; lambda*-defined procedures now throw an error by default if a
;; keyword other than one of those specified is found in the actual
;; passed arguments. However, specifying #&allow-other-keys
;; immediately after the kyword argument declarations restores the
;; previous behavior of ignoring unknown keywords. lambda* also now
;; guarantees that if the same keyword is passed more than once, the
;; last one passed is the one that takes effect. For example,
;; ((lambda* (#&key (heads 0) (tails 0)) (display (list heads tails)))
;; #:heads 37 #:tails 42 #:heads 99)
;; would result in (99 47) being displayed.
;;
;; #&rest is also now provided as a synonym for the dotted syntax rest
;; argument. The argument lists (a . b) and (a #&rest b) are equivalent in
;; all respects to lambda*. This is provided for more similarity to DSSSL,
;; MIT-Scheme and Kawa among others, as well as for refugees from other
;; Lisp dialects.
(defmacro-public lambda* (ARGLIST . BODY)
(parse-arglist
ARGLIST
(lambda (non-optional-args optionals keys aok? rest-arg)
; Check for syntax errors.
(if (not (every? symbol? non-optional-args))
(error "Syntax error in fixed argument declaration."))
(if (not (every? ext-decl? optionals))
(error "Syntax error in optional argument declaration."))
(if (not (every? ext-decl? keys))
(error "Syntax error in keyword argument declaration."))
(if (not (or (symbol? rest-arg) (eq? #f rest-arg)))
(error "Syntax error in rest argument declaration."))
;; generate the code.
(let ((rest-gensym (or rest-arg (gensym "lambda*:G"))))
(if (not (and (null? optionals) (null? keys)))
`(lambda (,@non-optional-args . ,rest-gensym)
;; Make sure that if the proc had a docstring, we put it
;; here where it will be visible.
,@(if (and (not (null? BODY))
(string? (car BODY)))
(list (car BODY))
'())
(let-optional*
,rest-gensym
,optionals
(let-keywords* ,rest-gensym
,aok?
,keys
,@(if (and (not rest-arg) (null? keys))
`((if (not (null? ,rest-gensym))
(error "Too many arguments.")))
'())
,@BODY)))
`(lambda (,@ARGLIST . ,(if rest-arg rest-arg '()))
,@BODY))))))
(define (every? pred lst)
(or (null? lst)
(and (pred (car lst))
(every? pred (cdr lst)))))
(define (ext-decl? obj)
(or (symbol? obj)
(and (list? obj) (= 2 (length obj)) (symbol? (car obj)))))
(define (parse-arglist arglist cont)
(define (split-list-at val lst cont)
(cond
((memq val lst)
=> (lambda (pos)
(if (memq val (cdr pos))
(error (with-output-to-string
(lambda ()
(map display `(,val
" specified more than once in argument list.")))))
(cont (reverse (cdr (memq val (reverse lst)))) (cdr pos) #t))))
(else (cont lst '() #f))))
(define (parse-opt-and-fixed arglist keys aok? rest cont)
(split-list-at
'#&optional arglist
(lambda (before after split?)
(if (and split? (null? after))
(error "#&optional specified but no optional arguments declared.")
(cont before after keys aok? rest)))))
(define (parse-keys arglist rest cont)
(split-list-at
'#&allow-other-keys arglist
(lambda (aok-before aok-after aok-split?)
(if (and aok-split? (not (null? aok-after)))
(error "#&allow-other-keys not at end of keyword argument declarations.")
(split-list-at
'#&key aok-before
(lambda (key-before key-after key-split?)
(cond
((and aok-split? (not key-split?))
(error "#&allow-other-keys specified but no keyword arguments declared."))
(key-split?
(cond
((null? key-after) (error "#&key specified but no keyword arguments declared."))
((memq '#&optional key-after) (error "#&optional arguments declared after #&key arguments."))
(else (parse-opt-and-fixed key-before key-after aok-split? rest cont))))
(else (parse-opt-and-fixed arglist '() #f rest cont)))))))))
(define (parse-rest arglist cont)
(cond
((not (pair? arglist)) (cont '() '() '() #f arglist))
((not (list? arglist))
(let* ((copy (list-copy arglist))
(lp (last-pair copy))
(ra (cdr lp)))
(set-cdr! lp '())
(if (memq '#&rest copy)
(error "Cannot specify both #&rest and dotted rest argument.")
(parse-keys copy ra cont))))
(else (split-list-at
'#&rest arglist
(lambda (before after split?)
(if split?
(case (length after)
((0) (error "#&rest not followed by argument."))
((1) (parse-keys before (car after) cont))
(else (error "#&rest argument must be declared last.")))
(parse-keys before #f cont)))))))
(parse-rest arglist cont))
;; define* args . body
;; define*-public args . body
;; define and define-public extended for optional and keyword arguments
;;
;; define* and define*-public support optional arguments with
;; a similar syntax to lambda*. They also support arbitrary-depth
;; currying, just like Guile's define. Some examples:
;; (define* (x y #&optional a (z 3) #&key w . u) (display (list y z u)))
;; defines a procedure x with a fixed argument y, an optional agument
;; a, another optional argument z with default value 3, a keyword argument w,
;; and a rest argument u.
;; (define-public* ((foo #&optional bar) #&optional baz) '())
;; This illustrates currying. A procedure foo is defined, which,
;; when called with an optional argument bar, returns a procedure that
;; takes an optional argument baz.
;;
;; Of course, define*[-public] also supports #&rest and #&allow-other-keys
;; in the same way as lambda*.
(defmacro-public define* (ARGLIST . BODY)
(define*-guts 'define ARGLIST BODY))
(defmacro-public define*-public (ARGLIST . BODY)
(define*-guts 'define-public ARGLIST BODY))
;; The guts of define* and define*-public.
(define (define*-guts DT ARGLIST BODY)
(define (nest-lambda*s arglists)
(if (null? arglists)
BODY
`((lambda* ,(car arglists) ,@(nest-lambda*s (cdr arglists))))))
(define (define*-guts-helper ARGLIST arglists)
(let ((first (car ARGLIST))
(al (cons (cdr ARGLIST) arglists)))
(if (symbol? first)
`(,DT ,first ,@(nest-lambda*s al))
(define*-guts-helper first al))))
(if (symbol? ARGLIST)
`(,DT ,ARGLIST ,@BODY)
(define*-guts-helper ARGLIST '())))
;; defmacro* name args . body
;; defmacro*-public args . body
;; defmacro and defmacro-public extended for optional and keyword arguments
;;
;; These are just like defmacro and defmacro-public except that they
;; take lambda*-style extended paramter lists, where #&optional,
;; #&key, #&allow-other-keys and #&rest are allowed with the usual
;; semantics. Here is an example of a macro with an optional argument:
;; (defmacro* transmorgify (a #&optional b)
(defmacro-public defmacro* (NAME ARGLIST . BODY)
(defmacro*-guts 'define NAME ARGLIST BODY))
(defmacro-public defmacro*-public (NAME ARGLIST . BODY)
(defmacro*-guts 'define-public NAME ARGLIST BODY))
;; The guts of defmacro* and defmacro*-public
(define (defmacro*-guts DT NAME ARGLIST BODY)
`(,DT ,NAME
(,(lambda (transformer) (defmacro:transformer transformer))
(lambda* ,ARGLIST ,@BODY))))