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141 lines
5.0 KiB
EmacsLisp
141 lines
5.0 KiB
EmacsLisp
;;; assoc.el --- insert/delete/sort functions on association lists
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;; Copyright (C) 1996 Free Software Foundation, Inc.
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;; Author: Barry A. Warsaw <bwarsaw@cen.com>
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;; Keywords: extensions
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software; you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation; either version 2, or (at your option)
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;; any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs; see the file COPYING. If not, write to the
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;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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;; Boston, MA 02111-1307, USA.
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;;; Commentary:
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;; Association list utilities providing insertion, deletion, sorting
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;; fetching off key-value pairs in association lists.
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;;; Code:
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(defun asort (alist-symbol key)
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"Move a specified key-value pair to the head of an alist.
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The alist is referenced by ALIST-SYMBOL. Key-value pair to move to
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head is one matching KEY. Returns the sorted list and doesn't affect
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the order of any other key-value pair. Side effect sets alist to new
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sorted list."
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(set alist-symbol
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(sort (copy-alist (eval alist-symbol))
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(function (lambda (a b) (equal (car a) key))))))
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(defun aelement (key value)
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"Makes a list of a cons cell containing car of KEY and cdr of VALUE.
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The returned list is suitable as an element of an alist."
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(list (cons key value)))
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(defun aheadsym (alist)
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"Return the key symbol at the head of ALIST."
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(car (car alist)))
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(defun anot-head-p (alist key)
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"Find out if a specified key-value pair is not at the head of an alist.
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The alist to check is specified by ALIST and the key-value pair is the
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one matching the supplied KEY. Returns nil if ALIST is nil, or if
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key-value pair is at the head of the alist. Returns t if key-value
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pair is not at the head of alist. ALIST is not altered."
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(not (equal (aheadsym alist) key)))
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(defun aput (alist-symbol key &optional value)
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"Inserts a key-value pair into an alist.
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The alist is referenced by ALIST-SYMBOL. The key-value pair is made
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from KEY and optionally, VALUE. Returns the altered alist or nil if
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ALIST is nil.
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If the key-value pair referenced by KEY can be found in the alist, and
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VALUE is supplied non-nil, then the value of KEY will be set to VALUE.
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If VALUE is not supplied, or is nil, the key-value pair will not be
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modified, but will be moved to the head of the alist. If the key-value
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pair cannot be found in the alist, it will be inserted into the head
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of the alist (with value nil if VALUE is nil or not supplied)."
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(let ((elem (aelement key value))
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alist)
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(asort alist-symbol key)
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(setq alist (eval alist-symbol))
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(cond ((null alist) (set alist-symbol elem))
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((anot-head-p alist key) (set alist-symbol (nconc elem alist)))
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(value (setcar alist (car elem)))
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(t alist))))
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(defun adelete (alist-symbol key)
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"Delete a key-value pair from the alist.
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Alist is referenced by ALIST-SYMBOL and the key-value pair to remove
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is pair matching KEY. Returns the altered alist."
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(asort alist-symbol key)
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(let ((alist (eval alist-symbol)))
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(cond ((null alist) nil)
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((anot-head-p alist key) alist)
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(t (set alist-symbol (cdr alist))))))
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(defun aget (alist key &optional keynil-p)
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"Returns the value in ALIST that is associated with KEY.
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Optional KEYNIL-P describes what to do if the value associated with
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KEY is nil. If KEYNIL-P is not supplied or is nil, and the value is
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nil, then KEY is returned. If KEYNIL-P is non-nil, then nil would be
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returned.
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If no key-value pair matching KEY could be found in ALIST, or ALIST is
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nil then nil is returned. ALIST is not altered."
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(let ((copy (copy-alist alist)))
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(cond ((null alist) nil)
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((progn (asort 'copy key)
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(anot-head-p copy key)) nil)
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((cdr (car copy)))
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(keynil-p nil)
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((car (car copy)))
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(t nil))))
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(defun amake (alist-symbol keylist &optional valuelist)
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"Make an association list.
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The association list is attached to the alist referenced by
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ALIST-SYMBOL. Each element in the KEYLIST becomes a key and is
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associated with the value in VALUELIST with the same index. If
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VALUELIST is not supplied or is nil, then each key in KEYLIST is
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associated with nil.
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KEYLIST and VALUELIST should have the same number of elements, but
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this isn't enforced. If VALUELIST is smaller than KEYLIST, remaining
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keys are associated with nil. If VALUELIST is larger than KEYLIST,
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extra values are ignored. Returns the created alist."
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(let ((keycar (car keylist))
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(keycdr (cdr keylist))
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(valcar (car valuelist))
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(valcdr (cdr valuelist)))
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(cond ((null keycdr)
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(aput alist-symbol keycar valcar))
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(t
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(amake alist-symbol keycdr valcdr)
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(aput alist-symbol keycar valcar))))
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(eval alist-symbol))
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(provide 'assoc)
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;;; assoc.el ends here
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