Created
December 9, 2013 21:17
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(import (rnrs) | |
(for (only (srfi :1) break) expand)) | |
(define-syntax foo | |
(lambda (stx) | |
(define (no-vals f befores) | |
(let ((temps (generate-temporaries befores))) | |
#`(lambda #,temps | |
(#,f #,@(map list befores temps))))) | |
(define (yes-vals f befores afters) | |
(let ((temps-before (generate-temporaries befores)) | |
(temps-after (generate-temporaries afters))) | |
#`(lambda #,temps-before | |
(let-values ((#,temps-after | |
(#,f #,@(map list befores temps-before)))) | |
(values #,@(map list afters temps-after)))))) | |
(syntax-case stx () | |
[(_ function converter ...) | |
(let-values (((before after) | |
(break (lambda (x) (free-identifier=? x #'::)) | |
#'(converter ...)))) | |
(if (null? after) | |
(no-vals #'function before) | |
(yes-vals #'function before (cdr after))))]))) | |
;; (foo cons 1+ 1+) | |
;; -> (lambda (x y) (cons (1+ x) (1+ y))) | |
;; (foo break identity cdr :: car car) | |
;; -> (lambda (f l) | |
;; (let-values (((a b) (break (identity f) (cdr l)))) | |
;; (values (car a) (car b)))) |
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