mirror/guile
mirror/guile
1
Fork 0
mirror of https://git.savannah.gnu.org/git/guile.git synced 2025-05-20 11:40:18 +02:00
Code Activity

srfi-16 just re-exports psyntax's case-lambda

Browse source 
* module/srfi/srfi-16.scm (case-lambda): Just re-export the core's
  case-lambda, it's semantically the same but faster and better
  integrated.
This commit is contained in:
Andy Wingo 2009-10-25 13:19:11 +01:00
parent 647117cd35
commit 9a8eb5fb46
1 changed files with 3 additions and 76 deletions
Download patch file Download diff file Expand all files Collapse all files

79
module/srfi/srfi-16.scm
View file

@ -46,81 +46,8 @@
;;; Code:
(define-module (srfi srfi-16)
#:replace (case-lambda))
#:re-export (case-lambda))
;; Case-lambda is now provided by code psyntax.
(cond-expand-provide (current-module) '(srfi-16))
(define-macro (case-lambda . clauses)
;; Return the length of the list @var{l}, but allow dotted list.
;;
(define (alength l)
(cond ((null? l) 0)
((pair? l) (+ 1 (alength (cdr l))))
(else 0)))
;; Return @code{#t} if @var{l} is a dotted list, @code{#f} if it is
;; a normal list.
;;
(define (dotted? l)
(cond ((null? l) #f)
((pair? l) (dotted? (cdr l)))
(else #t)))
;; Return the expression for accessing the @var{index}th element of
;; the list called @var{args-name}. If @var{tail?} is true, code
;; for accessing the list-tail is generated, otherwise for accessing
;; the list element itself.
;;
(define (accessor args-name index tail?)
(if tail?
(case index
((0) `,args-name)
((1) `(cdr ,args-name))
((2) `(cddr ,args-name))
((3) `(cdddr ,args-name))
((4) `(cddddr ,args-name))
(else `(list-tail ,args-name ,index)))
(case index
((0) `(car ,args-name))
((1) `(cadr ,args-name))
((2) `(caddr ,args-name))
((3) `(cadddr ,args-name))
(else `(list-ref ,args-name ,index)))))
;; Generate the binding lists of the variables of one case-lambda
;; clause. @var{vars} is the (possibly dotted) list of variables
;; and @var{args-name} is the generated name used for the argument
;; list.
;;
(define (gen-temps vars args-name)
(let lp ((v vars) (i 0))
(cond ((null? v) '())
((pair? v)
(cons `(,(car v) ,(accessor args-name i #f))
(lp (cdr v) (+ i 1))))
(else `((,v ,(accessor args-name i #t)))))))
;; Generate the cond clauses for each of the clauses of case-lambda,
;; including the parameter count check, binding of the parameters
;; and the code of the corresponding body.
;;
(define (gen-clauses l length-name args-name)
(cond ((null? l) (list '(else (error "too few arguments"))))
(else
(cons
`((,(if (dotted? (caar l)) '>= '=)
,length-name ,(alength (caar l)))
(let ,(gen-temps (caar l) args-name)
,@(cdar l)))
(gen-clauses (cdr l) length-name args-name)))))
(let ((args-name (gensym))
(length-name (gensym)))
(let ((proc
`(lambda ,args-name
(let ((,length-name (length ,args-name)))
(cond ,@(gen-clauses clauses length-name args-name))))))
proc)))
;;; srfi-16.scm ends here