* module/srfi/srfi-26.scm (cut, cute): Implement using `syntax-case'. The new implementation is mostly just a transcription of the old code; the reference implementation which relies only on `syntax-rules' may (or may not) be considered more elegant :-).
From: Andreas Rottmann <a.rottm...@gmx.at> Subject: Get rid of `define-macro' in the SRFI 26 implementation * module/srfi/srfi-26.scm (cut, cute): Implement using `syntax-case'. The new implementation is mostly just a transcription of the old code; the reference implementation which relies only on `syntax-rules' may (or may not) be considered more elegant :-). --- module/srfi/srfi-26.scm | 69 +++++++++++++++++++++++++++++----------------- 1 files changed, 43 insertions(+), 26 deletions(-) diff --git a/module/srfi/srfi-26.scm b/module/srfi/srfi-26.scm index 324a5dc..4a9f441 100644 --- a/module/srfi/srfi-26.scm +++ b/module/srfi/srfi-26.scm @@ -1,6 +1,6 @@ ;;; srfi-26.scm --- specializing parameters without currying. -;; Copyright (C) 2002, 2006 Free Software Foundation, Inc. +;; Copyright (C) 2002, 2006, 2010 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 @@ -21,29 +21,46 @@ (cond-expand-provide (current-module) '(srfi-26)) -(define-macro (cut slot . slots) - (let loop ((slots (cons slot slots)) - (params '()) - (args '())) - (if (null? slots) - `(lambda ,(reverse! params) ,(reverse! args)) - (let ((s (car slots)) - (rest (cdr slots))) - (case s - ((<>) - (let ((var (gensym))) - (loop rest (cons var params) (cons var args)))) - ((<...>) - (if (pair? rest) - (error "<...> not on the end of cut expression")) - (let ((var (gensym))) - `(lambda ,(append! (reverse! params) var) - (apply ,@(reverse! (cons var args)))))) - (else - (loop rest params (cons s args)))))))) +(define-syntax cut + (lambda (stx) + (syntax-case stx () + ((cut slot0 slot1+ ...) + (let loop ((slots #'(slot0 slot1+ ...)) + (params '()) + (args '())) + (if (null? slots) + #`(lambda #,(reverse params) #,(reverse args)) + (let ((s (car slots)) + (rest (cdr slots))) + (with-syntax (((var) (generate-temporaries '(var)))) + (syntax-case s (<> <...>) + (<> + (loop rest (cons #'var params) (cons #'var args))) + (<...> + (if (pair? rest) + (error "<...> not on the end of cut expression")) + #`(lambda #,(append (reverse params) #'var) + (apply #,@(reverse (cons #'var args))))) + (else + (loop rest params (cons s args)))))))))))) -(define-macro (cute . slots) - (let ((temp (map (lambda (s) (and (not (memq s '(<> <...>))) (gensym))) - slots))) - `(let ,(delq! #f (map (lambda (t s) (and t (list t s))) temp slots)) - (cut ,@(map (lambda (t s) (or t s)) temp slots))))) +(define-syntax cute + (lambda (stx) + (syntax-case stx () + ((cute slots ...) + (let loop ((slots #'(slots ...)) + (bindings '()) + (arguments '())) + (define (process-hole) + (loop (cdr slots) bindings (cons (car slots) arguments))) + (if (null? slots) + #`(let #,bindings + (cut #,@(reverse arguments))) + (syntax-case (car slots) (<> <...>) + (<> (process-hole)) + (<...> (process-hole)) + (expr + (with-syntax (((t) (generate-temporaries '(t)))) + (loop (cdr slots) + (cons #'(t expr) bindings) + (cons #'t arguments))))))))))) -- tg: (c0f6c16..) t/srfi-26-hygienic (depends on: master)
Regards, Rotty -- Andreas Rottmann -- <http://rotty.yi.org/>
