diff options
| -rw-r--r-- | NEWS | 13 | ||||
| -rw-r--r-- | doc/ref/srfi-modules.texi | 22 | ||||
| -rw-r--r-- | module/srfi/Makefile.am | 3 | ||||
| -rw-r--r-- | module/srfi/srfi-71.scm | 265 |
4 files changed, 300 insertions, 3 deletions
@@ -1,11 +1,22 @@ Guile NEWS --- history of user-visible changes. -Copyright (C) 1996-2017 Free Software Foundation, Inc. +Copyright (C) 1996-2018 Free Software Foundation, Inc. See the end for copying conditions. Please send Guile bug reports to bug-guile@gnu.org. +Changes in 2.2.4 (since 2.2.3): + +* New interfaces and functionality + +** SRFI-71 (Extended LET-syntax for multiple values) + +Guile now includes SRFI-71, which extends let, let*, and letrec to +support assigning multiple values. See "SRFI-71" in the manual for +details. + + Changes in 2.2.3 (since 2.2.2): * New interfaces and functionality diff --git a/doc/ref/srfi-modules.texi b/doc/ref/srfi-modules.texi index 3d4415629..5d2ebe67c 100644 --- a/doc/ref/srfi-modules.texi +++ b/doc/ref/srfi-modules.texi @@ -1,6 +1,6 @@ @c -*-texinfo-*- @c This is part of the GNU Guile Reference Manual. -@c Copyright (C) 1996, 1997, 2000-2004, 2006, 2007-2014, 2017 +@c Copyright (C) 1996, 1997, 2000-2004, 2006, 2007-2014, 2017, 2018 @c Free Software Foundation, Inc. @c See the file guile.texi for copying conditions. @@ -58,6 +58,7 @@ get the relevant SRFI documents from the SRFI home page * SRFI-64:: A Scheme API for test suites. * SRFI-67:: Compare procedures * SRFI-69:: Basic hash tables. +* SRFI-71:: Extended let-syntax for multiple values. * SRFI-87:: => in case clauses. * SRFI-88:: Keyword objects. * SRFI-98:: Accessing environment variables. @@ -5399,6 +5400,25 @@ Answer a hash value appropriate for equality predicate @code{equal?}, @code{hash} is a backwards-compatible replacement for Guile's built-in @code{hash}. +@node SRFI-71 +@subsection SRFI-71 - Extended let-syntax for multiple values +@cindex SRFI-71 + +This SRFI shadows the forms for @code{let}, @code{let*}, and @code{letrec} +so that they may accept multiple values. For example: + +@example +(use-modules (srfi srfi-71)) + +(let* ((x y (values 1 2)) + (z (+ x y))) + (* z 2)) +@result{} 6 +@end example + +See @uref{http://srfi.schemers.org/srfi-71/srfi-71.html, the +specification of SRFI-71}. + @node SRFI-87 @subsection SRFI-87 => in case clauses @cindex SRFI-87 diff --git a/module/srfi/Makefile.am b/module/srfi/Makefile.am index 7cbac6630..8b7e965c5 100644 --- a/module/srfi/Makefile.am +++ b/module/srfi/Makefile.am @@ -1,6 +1,6 @@ ## Process this file with automake to produce Makefile.in. ## -## Copyright (C) 2000, 2004, 2006, 2008 Free Software Foundation, Inc. +## Copyright (C) 2000, 2004, 2006, 2008, 2017 Free Software Foundation, Inc. ## ## This file is part of GUILE. ## @@ -44,6 +44,7 @@ SOURCES = \ srfi-39.scm \ srfi-60.scm \ srfi-69.scm \ + srfi-71.scm \ srfi-88.scm # Will poke this later. diff --git a/module/srfi/srfi-71.scm b/module/srfi/srfi-71.scm new file mode 100644 index 000000000..8e8f4c77e --- /dev/null +++ b/module/srfi/srfi-71.scm @@ -0,0 +1,265 @@ +;; Copyright (c) 2005 Sebastian Egner. +;; +;; Permission is hereby granted, free of charge, to any person obtaining a +;; copy of this software and associated documentation files (the +;; ``Software''), to deal in the Software without restriction, including +;; without limitation the rights to use, copy, modify, merge, publish, +;; distribute, sublicense, and/or sell copies of the Software, and to +;; permit persons to whom the Software is furnished to do so, subject to +;; the following conditions: +;; +;; The above copyright notice and this permission notice shall be included +;; in all copies or substantial portions of the Software. +;; +;; THE SOFTWARE IS PROVIDED ``AS IS'', WITHOUT WARRANTY OF ANY KIND, +;; EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF +;; MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND +;; NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE +;; LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION +;; OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION +;; WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. + +;; Reference implementation of SRFI-71 using PLT 208's modules +;; Sebastian.Egner@philips.com, 2005-04-29 +;; +;; Adjusted for Guile module system by +;; Christopher Allan Webber <cwebber@dustycloud.org>, 2017-06-29 + +(define-module (srfi srfi-71) + #:export (uncons unlist unvector values->list + values->vector) + #:replace ((srfi-let . let) + (srfi-let* . let*) + (srfi-letrec . letrec))) + +(define-syntax r5rs-let + (syntax-rules () + ((r5rs-let ((v x) ...) body1 body ...) + (let ((v x) ...) body1 body ...)) + ((r5rs-let tag ((v x) ...) body1 body ...) + (let tag ((v x) ...) body1 body ...)))) + +(define-syntax r5rs-let* + (syntax-rules () + ((r5rs-let* ((v x) ...) body1 body ...) + (let* ((v x) ...) body1 body ...)))) + +(define-syntax r5rs-letrec + (syntax-rules () + ((r5rs-letrec ((v x) ...) body1 body ...) + (letrec ((v x) ...) body1 body ...)))) + +; --- textual copy of 'letvalues.scm' starts here --- + +; Reference implementation of SRFI-71 (generic part) +; Sebastian.Egner@philips.com, 20-May-2005, PLT 208 +; +; In order to avoid conflicts with the existing let etc. +; the macros defined here are called srfi-let etc., +; and they are defined in terms of r5rs-let etc. +; It is up to the actual implementation to save let/*/rec +; in r5rs-let/*/rec first and redefine let/*/rec +; by srfi-let/*/rec then. +; +; There is also a srfi-letrec* being defined (in view of R6RS.) +; +; Macros used internally are named i:<something>. +; +; Abbreviations for macro arguments: +; bs - <binding spec> +; b - component of a binding spec (values, <variable>, or <expression>) +; v - <variable> +; vr - <variable> for rest list +; x - <expression> +; t - newly introduced temporary variable +; vx - (<variable> <expression>) +; rec - flag if letrec is produced (and not let) +; cwv - call-with-value skeleton of the form (x formals) +; (call-with-values (lambda () x) (lambda formals /payload/)) +; where /payload/ is of the form (let (vx ...) body1 body ...). +; +; Remark (*): +; We bind the variables of a letrec to i:undefined since there is +; no portable (R5RS) way of binding a variable to a values that +; raises an error when read uninitialized. + +(define i:undefined 'undefined) + +(define-syntax srfi-letrec* ; -> srfi-letrec + (syntax-rules () + ((srfi-letrec* () body1 body ...) + (srfi-letrec () body1 body ...)) + ((srfi-letrec* (bs) body1 body ...) + (srfi-letrec (bs) body1 body ...)) + ((srfi-letrec* (bs1 bs2 bs ...) body1 body ...) + (srfi-letrec (bs1) (srfi-letrec* (bs2 bs ...) body1 body ...))))) + +(define-syntax srfi-letrec ; -> i:let + (syntax-rules () + ((srfi-letrec ((b1 b2 b ...) ...) body1 body ...) + (i:let "bs" #t () () (body1 body ...) ((b1 b2 b ...) ...))))) + +(define-syntax srfi-let* ; -> srfi-let + (syntax-rules () + ((srfi-let* () body1 body ...) + (srfi-let () body1 body ...)) + ((srfi-let* (bs) body1 body ...) + (srfi-let (bs) body1 body ...)) + ((srfi-let* (bs1 bs2 bs ...) body1 body ...) + (srfi-let (bs1) (srfi-let* (bs2 bs ...) body1 body ...))))) + +(define-syntax srfi-let ; -> i:let or i:named-let + (syntax-rules () + ((srfi-let ((b1 b2 b ...) ...) body1 body ...) + (i:let "bs" #f () () (body1 body ...) ((b1 b2 b ...) ...))) + ((srfi-let tag ((b1 b2 b ...) ...) body1 body ...) + (i:named-let tag () (body1 body ...) ((b1 b2 b ...) ...))))) + +(define-syntax i:let + (syntax-rules (values) + +; (i:let "bs" rec (cwv ...) (vx ...) body (bs ...)) +; processes the binding specs bs ... by adding call-with-values +; skeletons to cwv ... and bindings to vx ..., and afterwards +; wrapping the skeletons around the payload (let (vx ...) . body). + + ; no more bs to process -> wrap call-with-values skeletons + ((i:let "bs" rec (cwv ...) vxs body ()) + (i:let "wrap" rec vxs body cwv ...)) + + ; recognize form1 without variable -> dummy binding for side-effects + ((i:let "bs" rec cwvs (vx ...) body (((values) x) bs ...)) + (i:let "bs" rec cwvs (vx ... (dummy (begin x #f))) body (bs ...))) + + ; recognize form1 with single variable -> just extend vx ... + ((i:let "bs" rec cwvs (vx ...) body (((values v) x) bs ...)) + (i:let "bs" rec cwvs (vx ... (v x)) body (bs ...))) + + ; recognize form1 without rest arg -> generate cwv + ((i:let "bs" rec cwvs vxs body (((values v ...) x) bs ...)) + (i:let "form1" rec cwvs vxs body (bs ...) (x ()) (values v ...))) + + ; recognize form1 with rest arg -> generate cwv + ((i:let "bs" rec cwvs vxs body (((values . vs) x) bs ...)) + (i:let "form1+" rec cwvs vxs body (bs ...) (x ()) (values . vs))) + + ; recognize form2 with single variable -> just extend vx ... + ((i:let "bs" rec cwvs (vx ...) body ((v x) bs ...)) + (i:let "bs" rec cwvs (vx ... (v x)) body (bs ...))) + + ; recognize form2 with >=2 variables -> transform to form1 + ((i:let "bs" rec cwvs vxs body ((b1 b2 b3 b ...) bs ...)) + (i:let "form2" rec cwvs vxs body (bs ...) (b1 b2) (b3 b ...))) + +; (i:let "form1" rec cwvs vxs body bss (x (t ...)) (values v1 v2 v ...)) +; processes the variables in v1 v2 v ... adding them to (t ...) +; and producing a cwv when finished. There is not rest argument. + + ((i:let "form1" rec (cwv ...) vxs body bss (x ts) (values)) + (i:let "bs" rec (cwv ... (x ts)) vxs body bss)) + ((i:let "form1" rec cwvs (vx ...) body bss (x (t ...)) (values v1 v ...)) + (i:let "form1" rec cwvs (vx ... (v1 t1)) body bss (x (t ... t1)) (values v ...))) + +; (i:let "form1+" rec cwvs vxs body bss (x (t ...)) (values v ... . vr)) +; processes the variables in v ... . vr adding them to (t ...) +; and producing a cwv when finished. The rest arg is vr. + + ((i:let "form1+" rec cwvs (vx ...) body bss (x (t ...)) (values v1 v2 . vs)) + (i:let "form1+" rec cwvs (vx ... (v1 t1)) body bss (x (t ... t1)) (values v2 . vs))) + ((i:let "form1+" rec (cwv ...) (vx ...) body bss (x (t ...)) (values v1 . vr)) + (i:let "bs" rec (cwv ... (x (t ... t1 . tr))) (vx ... (v1 t1) (vr tr)) body bss)) + ((i:let "form1+" rec (cwv ...) (vx ...) body bss (x ()) (values . vr)) + (i:let "bs" rec (cwv ... (x tr)) (vx ... (vr tr)) body bss)) + +; (i:let "form2" rec cwvs vxs body bss (v ...) (b ... x)) +; processes the binding items (b ... x) from form2 as in +; (v ... b ... x) into ((values v ... b ...) x), i.e. form1. +; Then call "bs" recursively. + + ((i:let "form2" rec cwvs vxs body (bs ...) (v ...) (x)) + (i:let "bs" rec cwvs vxs body (((values v ...) x) bs ...))) + ((i:let "form2" rec cwvs vxs body bss (v ...) (b1 b2 b ...)) + (i:let "form2" rec cwvs vxs body bss (v ... b1) (b2 b ...))) + +; (i:let "wrap" rec ((v x) ...) (body ...) cwv ...) +; wraps cwv ... around the payload generating the actual code. +; For letrec this is of course different than for let. + + ((i:let "wrap" #f vxs body) + (r5rs-let vxs . body)) + ((i:let "wrap" #f vxs body (x formals) cwv ...) + (call-with-values + (lambda () x) + (lambda formals (i:let "wrap" #f vxs body cwv ...)))) + + ((i:let "wrap" #t vxs body) + (r5rs-letrec vxs . body)) + ((i:let "wrap" #t ((v t) ...) body cwv ...) + (r5rs-let ((v i:undefined) ...) ; (*) + (i:let "wraprec" ((v t) ...) body cwv ...))) + +; (i:let "wraprec" ((v t) ...) body cwv ...) +; generate the inner code for a letrec. The variables v ... +; are the user-visible variables (bound outside), and t ... +; are the temporary variables bound by the cwv consumers. + + ((i:let "wraprec" ((v t) ...) (body ...)) + (begin (set! v t) ... (r5rs-let () body ...))) + ((i:let "wraprec" vxs body (x formals) cwv ...) + (call-with-values + (lambda () x) + (lambda formals (i:let "wraprec" vxs body cwv ...)))) + + )) + +(define-syntax i:named-let + (syntax-rules (values) + +; (i:named-let tag (vx ...) body (bs ...)) +; processes the binding specs bs ... by extracting the variable +; and expression, adding them to vx and turning the result into +; an ordinary named let. + + ((i:named-let tag vxs body ()) + (r5rs-let tag vxs . body)) + ((i:named-let tag (vx ...) body (((values v) x) bs ...)) + (i:named-let tag (vx ... (v x)) body (bs ...))) + ((i:named-let tag (vx ...) body ((v x) bs ...)) + (i:named-let tag (vx ... (v x)) body (bs ...))))) + +; --- standard procedures --- + +(define (uncons pair) + (values (car pair) (cdr pair))) + +(define (uncons-2 list) + (values (car list) (cadr list) (cddr list))) + +(define (uncons-3 list) + (values (car list) (cadr list) (caddr list) (cdddr list))) + +(define (uncons-4 list) + (values (car list) (cadr list) (caddr list) (cadddr list) (cddddr list))) + +(define (uncons-cons alist) + (values (caar alist) (cdar alist) (cdr alist))) + +(define (unlist list) + (apply values list)) + +(define (unvector vector) + (apply values (vector->list vector))) + +; --- standard macros --- + +(define-syntax values->list + (syntax-rules () + ((values->list x) + (call-with-values (lambda () x) list)))) + +(define-syntax values->vector + (syntax-rules () + ((values->vector x) + (call-with-values (lambda () x) vector)))) + +; --- textual copy of 'letvalues.scm' ends here --- |