mes/module/srfi/srfi-1.scm

;;; From Guile-1.8

;; 	Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006 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.
;; 
;; This library is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
;; Lesser General Public License for more details.
;; 
;; You should have received a copy of the GNU Lesser General Public
;; License along with this library; if not, write to the Free Software
;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

;;; Author: Martin Grabmueller <mgrabmue@cs.tu-berlin.de>
;;; Date: 2001-06-06

;;; Searching

;; Internal helper procedure.  Map `f' over the single list `ls'.
;;
(define map1 map)

(define (any pred ls . lists)
  (if (null? lists)
      (any1 pred ls)
      (let lp ((lists (cons ls lists)))
	(cond ((any1 null? lists)
	       #f)
	      ((any1 null? (map1 cdr lists))
	       (apply pred (map1 car lists)))
	      (else
	       (or (apply pred (map1 car lists)) (lp (map1 cdr lists))))))))

(define (any1 pred ls)
  (let lp ((ls ls))
    (cond ((null? ls)
	   #f)
	  ((null? (cdr ls))
	   (pred (car ls)))
	  (else
	   (or (pred (car ls)) (lp (cdr ls)))))))

(define (every pred ls . lists)
  (if (null? lists)
      (every1 pred ls)
      (let lp ((lists (cons ls lists)))
	(cond ((any1 null? lists)
	       #t)
	      ((any1 null? (map1 cdr lists))
	       (apply pred (map1 car lists)))
	      (else
	       (and (apply pred (map1 car lists)) (lp (map1 cdr lists))))))))

(define (every1 pred ls)
  (let lp ((ls ls))
    (cond ((null? ls)
	   #t)
	  ((null? (cdr ls))
	   (pred (car ls)))
	  (else
	   (and (pred (car ls)) (lp (cdr ls)))))))

;;; Set operations on lists

(define (lset-union = . rest)
  (let ((acc '()))
    (for-each (lambda (lst)
		(if (null? acc)
		    (set! acc lst)
		    (for-each (lambda (elem)
				(if (not (member elem acc =))
				    (set! acc (cons elem acc))))
			      lst)))
	      rest)
    acc))

(define (lset-intersection = list1 . rest)
  (let lp ((l list1) (acc '()))
    (if (null? l)
      (reverse! acc)
      (if (every (lambda (ll) (member (car l) ll =)) rest)
	(lp (cdr l) (cons (car l) acc))
	(lp (cdr l) acc)))))

(define (lset-difference = list1 . rest)
  (if (null? rest)
    list1
    (let lp ((l list1) (acc '()))
      (if (null? l)
	(reverse! acc)
	(if (any (lambda (ll) (member (car l) ll =)) rest)
	  (lp (cdr l) acc)
	  (lp (cdr l) (cons (car l) acc)))))))