;;;
;;; <alist.ss> ---- Association list functions
;;; Time-stamp: <02/03/01 13:56:33 noel>
;;;
;;; Copyright (C) 2002 by Noel Welsh.
;;;
;;; This file is part of SRFI-1.

;;; SRFI-1 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.

;;; SRFI-1 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 SRFI-1; if not, write to the Free Software
;;; Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA

;;; Author: Noel Welsh <noelwelsh@yahoo.com>
;;
;;
;; Commentary:

;; Based on the reference implementation by Olin Shiver and hence:

;; Copyright (c) 1998, 1999 by Olin Shivers. You may do as you please with
;; this code as long as you do not remove this copyright notice or
;; hold me liable for its use. Please send bug reports to shivers@ai.mit.edu.
;;     -Olin

#lang scheme/base

(require (only-in "search.ss" find))

(provide (rename-out [my-assoc assoc])
         alist-cons
         alist-copy
         alist-delete
         #; alist-delete! ; lists are immutable
         )

;; Extended from R4RS to take an optional comparison argument.
(define (my-assoc x lis [= equal?])
  (find (lambda (entry) (= x (car entry))) lis))

(define (alist-cons key datum alist) (cons (cons key datum) alist))

(define (alist-copy alist)
  (map (lambda (elt) (cons (car elt) (cdr elt))) alist))

(define (alist-delete key alist [= equal?])
  (filter (lambda (elt) (not (= key (car elt)))) alist))

#; ; lists are immutable
(define (alist-delete! key alist [= equal?])
  (filter! (lambda (elt) (not (= key (car elt)))) alist))

;;; alist.ss ends here