1 ;;; assoc.el --- insert/delete/sort functions on association lists
3 ;; Copyright (C) 1996, 2001, 2002, 2003, 2004, 2005,
4 ;; 2006, 2007, 2008 Free Software Foundation, Inc.
6 ;; Author: Barry A. Warsaw <bwarsaw@cen.com>
7 ;; Keywords: extensions
9 ;; This file is part of GNU Emacs.
11 ;; GNU Emacs is free software: you can redistribute it and/or modify
12 ;; it under the terms of the GNU General Public License as published by
13 ;; the Free Software Foundation, either version 3 of the License, or
14 ;; (at your option) any later version.
16 ;; GNU Emacs is distributed in the hope that it will be useful,
17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 ;; GNU General Public License for more details.
21 ;; You should have received a copy of the GNU General Public License
22 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
26 ;; Association list utilities providing insertion, deletion, sorting
27 ;; fetching off key-value pairs in association lists.
31 (defun asort (alist-symbol key
)
32 "Move a specified key-value pair to the head of an alist.
33 The alist is referenced by ALIST-SYMBOL. Key-value pair to move to
34 head is one matching KEY. Returns the sorted list and doesn't affect
35 the order of any other key-value pair. Side effect sets alist to new
38 (sort (copy-alist (eval alist-symbol
))
39 (function (lambda (a b
) (equal (car a
) key
))))))
42 (defun aelement (key value
)
43 "Makes a list of a cons cell containing car of KEY and cdr of VALUE.
44 The returned list is suitable as an element of an alist."
45 (list (cons key value
)))
48 (defun aheadsym (alist)
49 "Return the key symbol at the head of ALIST."
53 (defun anot-head-p (alist key
)
54 "Find out if a specified key-value pair is not at the head of an alist.
55 The alist to check is specified by ALIST and the key-value pair is the
56 one matching the supplied KEY. Returns nil if ALIST is nil, or if
57 key-value pair is at the head of the alist. Returns t if key-value
58 pair is not at the head of alist. ALIST is not altered."
59 (not (equal (aheadsym alist
) key
)))
62 (defun aput (alist-symbol key
&optional value
)
63 "Inserts a key-value pair into an alist.
64 The alist is referenced by ALIST-SYMBOL. The key-value pair is made
65 from KEY and optionally, VALUE. Returns the altered alist or nil if
68 If the key-value pair referenced by KEY can be found in the alist, and
69 VALUE is supplied non-nil, then the value of KEY will be set to VALUE.
70 If VALUE is not supplied, or is nil, the key-value pair will not be
71 modified, but will be moved to the head of the alist. If the key-value
72 pair cannot be found in the alist, it will be inserted into the head
73 of the alist (with value nil if VALUE is nil or not supplied)."
74 (let ((elem (aelement key value
))
76 (asort alist-symbol key
)
77 (setq alist
(eval alist-symbol
))
78 (cond ((null alist
) (set alist-symbol elem
))
79 ((anot-head-p alist key
) (set alist-symbol
(nconc elem alist
)))
80 (value (setcar alist
(car elem
)))
84 (defun adelete (alist-symbol key
)
85 "Delete a key-value pair from the alist.
86 Alist is referenced by ALIST-SYMBOL and the key-value pair to remove
87 is pair matching KEY. Returns the altered alist."
88 (asort alist-symbol key
)
89 (let ((alist (eval alist-symbol
)))
90 (cond ((null alist
) nil
)
91 ((anot-head-p alist key
) alist
)
92 (t (set alist-symbol
(cdr alist
))))))
95 (defun aget (alist key
&optional keynil-p
)
96 "Returns the value in ALIST that is associated with KEY.
97 Optional KEYNIL-P describes what to do if the value associated with
98 KEY is nil. If KEYNIL-P is not supplied or is nil, and the value is
99 nil, then KEY is returned. If KEYNIL-P is non-nil, then nil would be
102 If no key-value pair matching KEY could be found in ALIST, or ALIST is
103 nil then nil is returned. ALIST is not altered."
104 (let ((copy (copy-alist alist
)))
105 (cond ((null alist
) nil
)
106 ((progn (asort 'copy key
)
107 (anot-head-p copy key
)) nil
)
114 (defun amake (alist-symbol keylist
&optional valuelist
)
115 "Make an association list.
116 The association list is attached to the alist referenced by
117 ALIST-SYMBOL. Each element in the KEYLIST becomes a key and is
118 associated with the value in VALUELIST with the same index. If
119 VALUELIST is not supplied or is nil, then each key in KEYLIST is
122 KEYLIST and VALUELIST should have the same number of elements, but
123 this isn't enforced. If VALUELIST is smaller than KEYLIST, remaining
124 keys are associated with nil. If VALUELIST is larger than KEYLIST,
125 extra values are ignored. Returns the created alist."
126 (let ((keycar (car keylist
))
127 (keycdr (cdr keylist
))
128 (valcar (car valuelist
))
129 (valcdr (cdr valuelist
)))
131 (aput alist-symbol keycar valcar
))
133 (amake alist-symbol keycdr valcdr
)
134 (aput alist-symbol keycar valcar
))))
139 ;; arch-tag: 3e58bd89-d912-4b74-a0dc-6ed9735922bc
140 ;;; assoc.el ends here