module/srfi/srfi-26.scm

   1 ;;; srfi-26.scm --- specializing parameters without currying.
   2
   3 ;; Copyright (C) 2002, 2006 Free Software Foundation, Inc.
   4 ;;
   5 ;; This library is free software; you can redistribute it and/or
   6 ;; modify it under the terms of the GNU Lesser General Public
   7 ;; License as published by the Free Software Foundation; either
   8 ;; version 2.1 of the License, or (at your option) any later version.
   9 ;;
  10 ;; This library is distributed in the hope that it will be useful,
  11 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13 ;; Lesser General Public License for more details.
  14 ;;
  15 ;; You should have received a copy of the GNU Lesser General Public
  16 ;; License along with this library; if not, write to the Free Software
  17 ;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  18
  19 (define-module (srfi srfi-26)
  20   :export (cut cute))
  21
  22 (cond-expand-provide (current-module) '(srfi-26))
  23
  24 (define-macro (cut slot . slots)
  25   (let loop ((slots     (cons slot slots))
  26              (params    '())
  27              (args      '()))
  28     (if (null? slots)
  29         `(lambda ,(reverse! params) ,(reverse! args))
  30       (let ((s    (car slots))
  31             (rest (cdr slots)))
  32         (case s
  33           ((<>)
  34            (let ((var (gensym)))
  35              (loop rest (cons var params) (cons var args))))
  36           ((<...>)
  37            (if (pair? rest)
  38                (error "<...> not on the end of cut expression"))
  39            (let ((var (gensym)))
  40              `(lambda ,(append! (reverse! params) var)
  41                 (apply ,@(reverse! (cons var args))))))
  42           (else
  43            (loop rest params (cons s args))))))))
  44
  45 (define-macro (cute . slots)
  46   (let ((temp (map (lambda (s) (and (not (memq s '(<> <...>))) (gensym)))
  47                    slots)))
  48     `(let ,(delq! #f (map (lambda (t s) (and t (list t s))) temp slots))
  49        (cut ,@(map (lambda (t s) (or t s)) temp slots)))))