diff options
Diffstat (limited to 'module/srfi/srfi-11.scm')
-rw-r--r-- | module/srfi/srfi-11.scm | 218 |
1 files changed, 55 insertions, 163 deletions
diff --git a/module/srfi/srfi-11.scm b/module/srfi/srfi-11.scm index 9e17d6632..22bda21a2 100644 --- a/module/srfi/srfi-11.scm +++ b/module/srfi/srfi-11.scm @@ -1,11 +1,11 @@ ;;; srfi-11.scm --- let-values and let*-values -;; Copyright (C) 2000, 2001, 2002, 2004, 2006 Free Software Foundation, Inc. +;; Copyright (C) 2000, 2001, 2002, 2004, 2006, 2009 Free Software Foundation, Inc. ;; ;; This library is free software; you can redistribute it and/or ;; modify it under the terms of the GNU Lesser General Public ;; License as published by the Free Software Foundation; either -;; version 2.1 of the License, or (at your option) any later version. +;; version 3 of the License, or (at your option) any later version. ;; ;; This library is distributed in the hope that it will be useful, ;; but WITHOUT ANY WARRANTY; without even the implied warranty of @@ -37,7 +37,6 @@ ;;; Code: (define-module (srfi srfi-11) - :use-module (ice-9 syncase) :export-syntax (let-values let*-values)) (cond-expand-provide (current-module) '(srfi-11)) @@ -64,148 +63,58 @@ ;; (q <tmp-q>)) ;; (baz x y z p q)))))) -;; I originally wrote this as a define-macro, but then I found out -;; that guile's gensym/gentemp was broken, so I tried rewriting it as -;; a syntax-rules statement. -;; [make-symbol now fixes gensym/gentemp problems.] -;; -;; Since syntax-rules didn't seem powerful enough to implement -;; let-values in one definition without exposing illegal syntax (or -;; perhaps my brain's just not powerful enough :>). I tried writing -;; it using a private helper, but that didn't work because the -;; let-values expands outside the scope of this module. I wonder why -;; syntax-rules wasn't designed to allow "private" patterns or -;; similar... -;; -;; So in the end, I dumped the syntax-rules implementation, reproduced -;; here for posterity, and went with the define-macro one below -- -;; gensym/gentemp's got to be fixed anyhow... -; -; (define-syntax let-values-helper -; (syntax-rules () -; ;; Take the vars from one let binding (i.e. the (x y z) from ((x y -; ;; z) (values 1 2 3)) and turn it in to the corresponding (lambda -; ;; (<tmp-x> <tmp-y> <tmp-z>) ...) from above, keeping track of the -; ;; temps you create so you can use them later... -; ;; -; ;; I really don't fully understand why the (var-1 var-1) trick -; ;; works below, but basically, when all those (x x) bindings show -; ;; up in the final "let", syntax-rules forces a renaming. - -; ((_ "consumer" () lambda-tmps final-let-bindings lv-bindings -; body ...) -; (lambda lambda-tmps -; (let-values-helper "cwv" lv-bindings final-let-bindings body ...))) - -; ((_ "consumer" (var-1 var-2 ...) (lambda-tmp ...) final-let-bindings lv-bindings -; body ...) -; (let-values-helper "consumer" -; (var-2 ...) -; (lambda-tmp ... var-1) -; ((var-1 var-1) . final-let-bindings) -; lv-bindings -; body ...)) - -; ((_ "cwv" () final-let-bindings body ...) -; (let final-let-bindings -; body ...)) - -; ((_ "cwv" ((vars-1 binding-1) other-bindings ...) final-let-bindings -; body ...) -; (call-with-values (lambda () binding-1) -; (let-values-helper "consumer" -; vars-1 -; () -; final-let-bindings -; (other-bindings ...) -; body ...))))) -; -; (define-syntax let-values -; (syntax-rules () -; ((let-values () body ...) -; (begin body ...)) -; ((let-values (binding ...) body ...) -; (let-values-helper "cwv" (binding ...) () body ...)))) -; -; -; (define-syntax let-values -; (letrec-syntax ((build-consumer -; ;; Take the vars from one let binding (i.e. the (x -; ;; y z) from ((x y z) (values 1 2 3)) and turn it -; ;; in to the corresponding (lambda (<tmp-x> <tmp-y> -; ;; <tmp-z>) ...) from above. -; (syntax-rules () -; ((_ () new-tmps tmp-vars () body ...) -; (lambda new-tmps -; body ...)) -; ((_ () new-tmps tmp-vars vars body ...) -; (lambda new-tmps -; (lv-builder vars tmp-vars body ...))) -; ((_ (var-1 var-2 ...) new-tmps tmp-vars vars body ...) -; (build-consumer (var-2 ...) -; (tmp-1 . new-tmps) -; ((var-1 tmp-1) . tmp-vars) -; bindings -; body ...)))) -; (lv-builder -; (syntax-rules () -; ((_ () tmp-vars body ...) -; (let tmp-vars -; body ...)) -; ((_ ((vars-1 binding-1) (vars-2 binding-2) ...) -; tmp-vars -; body ...) -; (call-with-values (lambda () binding-1) -; (build-consumer vars-1 -; () -; tmp-vars -; ((vars-2 binding-2) ...) -; body ...)))))) -; -; (syntax-rules () -; ((_ () body ...) -; (begin body ...)) -; ((_ ((vars binding) ...) body ...) -; (lv-builder ((vars binding) ...) () body ...))))) - -(define-macro (let-values vars . body) - - (define (map-1-dot proc elts) - ;; map over one optionally dotted (a b c . d) list, producing an - ;; optionally dotted result. - (cond - ((null? elts) '()) - ((pair? elts) (cons (proc (car elts)) (map-1-dot proc (cdr elts)))) - (else (proc elts)))) - - (define (undot-list lst) - ;; produce a non-dotted list from a possibly dotted list. - (cond - ((null? lst) '()) - ((pair? lst) (cons (car lst) (undot-list (cdr lst)))) - (else (list lst)))) - - (define (let-values-helper vars body prev-let-vars) - (let* ((var-binding (car vars)) - (new-tmps (map-1-dot (lambda (sym) (make-symbol "let-values-var")) - (car var-binding))) - (let-vars (map (lambda (sym tmp) (list sym tmp)) - (undot-list (car var-binding)) - (undot-list new-tmps)))) - - (if (null? (cdr vars)) - `(call-with-values (lambda () ,(cadr var-binding)) - (lambda ,new-tmps - (let ,(apply append let-vars prev-let-vars) - ,@body))) - `(call-with-values (lambda () ,(cadr var-binding)) - (lambda ,new-tmps - ,(let-values-helper (cdr vars) body - (cons let-vars prev-let-vars))))))) - - (if (null? vars) - `(begin ,@body) - (let-values-helper vars body '()))) +;; We could really use quasisyntax here... +(define-syntax let-values + (lambda (x) + (syntax-case x () + ((_ ((binds exp)) b0 b1 ...) + (syntax (call-with-values (lambda () exp) + (lambda binds b0 b1 ...)))) + ((_ (clause ...) b0 b1 ...) + (let lp ((clauses (syntax (clause ...))) + (ids '()) + (tmps '())) + (if (null? clauses) + (with-syntax (((id ...) ids) + ((tmp ...) tmps)) + (syntax (let ((id tmp) ...) + b0 b1 ...))) + (syntax-case (car clauses) () + (((var ...) exp) + (with-syntax (((new-tmp ...) (generate-temporaries + (syntax (var ...)))) + ((id ...) ids) + ((tmp ...) tmps)) + (with-syntax ((inner (lp (cdr clauses) + (syntax (var ... id ...)) + (syntax (new-tmp ... tmp ...))))) + (syntax (call-with-values (lambda () exp) + (lambda (new-tmp ...) inner)))))) + ((vars exp) + (with-syntax ((((new-tmp . new-var) ...) + (let lp ((vars (syntax vars))) + (syntax-case vars () + ((id . rest) + (acons (syntax id) + (car + (generate-temporaries (syntax (id)))) + (lp (syntax rest)))) + (id (acons (syntax id) + (car + (generate-temporaries (syntax (id)))) + '()))))) + ((id ...) ids) + ((tmp ...) tmps)) + (with-syntax ((inner (lp (cdr clauses) + (syntax (new-var ... id ...)) + (syntax (new-tmp ... tmp ...)))) + (args (let lp ((tmps (syntax (new-tmp ...)))) + (syntax-case tmps () + ((id) (syntax id)) + ((id . rest) (cons (syntax id) + (lp (syntax rest)))))))) + (syntax (call-with-values (lambda () exp) + (lambda args inner))))))))))))) ;;;;;;;;;;;;;; ;; let*-values @@ -227,28 +136,11 @@ (define-syntax let*-values (syntax-rules () ((let*-values () body ...) - (begin body ...)) + (let () body ...)) ((let*-values ((vars-1 binding-1) (vars-2 binding-2) ...) body ...) (call-with-values (lambda () binding-1) (lambda vars-1 (let*-values ((vars-2 binding-2) ...) body ...)))))) -; Alternate define-macro implementation... -; -; (define-macro (let*-values vars . body) -; (define (let-values-helper vars body) -; (let ((var-binding (car vars))) -; (if (null? (cdr vars)) -; `(call-with-values (lambda () ,(cadr var-binding)) -; (lambda ,(car var-binding) -; ,@body)) -; `(call-with-values (lambda () ,(cadr var-binding)) -; (lambda ,(car var-binding) -; ,(let-values-helper (cdr vars) body)))))) - -; (if (null? vars) -; `(begin ,@body) -; (let-values-helper vars body))) - ;;; srfi-11.scm ends here |