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135 lines
5.1 KiB
EmacsLisp
135 lines
5.1 KiB
EmacsLisp
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;; -*- Mode: Emacs-Lisp -*-
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;; sc-alist.el -- Version 1.0 (used to be baw-alist.el)
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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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;; ========== Disclaimer ==========
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;; This software is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY. No author or distributor accepts
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;; responsibility to anyone for the consequences of using it or for
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;; whether it serves any particular purpose or works at all, unless he
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;; says so in writing.
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;; This software was written as part of the supercite author's
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;; official duty as an employee of the United States Government and is
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;; thus in the public domain. You are free to use that particular
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;; software as you wish, but WITHOUT ANY WARRANTY WHATSOEVER. It
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;; would be nice, though if when you use any of this code, you give
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;; due credit to the author.
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;; ========== Author (unless otherwise stated) ========================
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;; NAME: Barry A. Warsaw USMAIL: Century Computing, Inc.
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;; TELE: (301) 593-3330 1014 West Street
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;; INET: bwarsaw@cen.com Laurel, Md 20707
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;; UUCP: uunet!cen.com!bwarsaw
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;;
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(provide 'sc-alist)
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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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