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1 | ;;; assoc.el --- insert/delete/sort functions on association lists |
2 | ||
d59c3137 | 3 | ;; Copyright (C) 1996, 2001, 2002, 2003, 2004, 2005, |
114f9c96 | 4 | ;; 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc. |
b578f267 | 5 | |
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6 | ;; Author: Barry A. Warsaw <bwarsaw@cen.com> |
7 | ;; Keywords: extensions | |
8 | ||
b578f267 EN |
9 | ;; This file is part of GNU Emacs. |
10 | ||
d6cba7ae | 11 | ;; GNU Emacs is free software: you can redistribute it and/or modify |
b578f267 | 12 | ;; it under the terms of the GNU General Public License as published by |
d6cba7ae GM |
13 | ;; the Free Software Foundation, either version 3 of the License, or |
14 | ;; (at your option) any later version. | |
b578f267 EN |
15 | |
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. | |
20 | ||
21 | ;; You should have received a copy of the GNU General Public License | |
d6cba7ae | 22 | ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. |
cdccfc0d ER |
23 | |
24 | ;;; Commentary: | |
25 | ||
26 | ;; Association list utilities providing insertion, deletion, sorting | |
27 | ;; fetching off key-value pairs in association lists. | |
28 | ||
29 | ;;; Code: | |
30 | ||
6476a5fa | 31 | (defun asort (alist-symbol key) |
cdccfc0d | 32 | "Move a specified key-value pair to the head of an alist. |
6cda144f | 33 | The alist is referenced by ALIST-SYMBOL. Key-value pair to move to |
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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 | |
36 | sorted list." | |
37 | (set alist-symbol | |
38 | (sort (copy-alist (eval alist-symbol)) | |
39 | (function (lambda (a b) (equal (car a) key)))))) | |
40 | ||
41 | ||
42 | (defun aelement (key value) | |
6cda144f | 43 | "Make a list of a cons cell containing car of KEY and cdr of VALUE. |
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44 | The returned list is suitable as an element of an alist." |
45 | (list (cons key value))) | |
46 | ||
47 | ||
48 | (defun aheadsym (alist) | |
49 | "Return the key symbol at the head of ALIST." | |
50 | (car (car alist))) | |
51 | ||
52 | ||
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))) | |
60 | ||
61 | ||
62 | (defun aput (alist-symbol key &optional value) | |
63 | "Inserts a key-value pair into an alist. | |
6cda144f JB |
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 | |
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66 | ALIST is nil. |
67 | ||
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 | |
6cda144f | 71 | modified, but will be moved to the head of the alist. If the key-value |
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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)) | |
75 | alist) | |
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))) | |
81 | (t alist)))) | |
82 | ||
83 | ||
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)))))) | |
93 | ||
94 | ||
95 | (defun aget (alist key &optional keynil-p) | |
6cda144f | 96 | "Return the value in ALIST that is associated with KEY. |
cdccfc0d ER |
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 | |
100 | returned. | |
101 | ||
102 | If no key-value pair matching KEY could be found in ALIST, or ALIST is | |
6cda144f | 103 | nil then nil is returned. ALIST is not altered." |
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104 | (let ((copy (copy-alist alist))) |
105 | (cond ((null alist) nil) | |
106 | ((progn (asort 'copy key) | |
107 | (anot-head-p copy key)) nil) | |
108 | ((cdr (car copy))) | |
109 | (keynil-p nil) | |
110 | ((car (car copy))) | |
111 | (t nil)))) | |
112 | ||
113 | ||
114 | (defun amake (alist-symbol keylist &optional valuelist) | |
115 | "Make an association list. | |
116 | The association list is attached to the alist referenced by | |
6cda144f JB |
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 | |
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119 | VALUELIST is not supplied or is nil, then each key in KEYLIST is |
120 | associated with nil. | |
121 | ||
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))) | |
130 | (cond ((null keycdr) | |
131 | (aput alist-symbol keycar valcar)) | |
132 | (t | |
133 | (amake alist-symbol keycdr valcdr) | |
134 | (aput alist-symbol keycar valcar)))) | |
135 | (eval alist-symbol)) | |
136 | ||
137 | (provide 'assoc) | |
138 | ||
cbee283d | 139 | ;; arch-tag: 3e58bd89-d912-4b74-a0dc-6ed9735922bc |
cdccfc0d | 140 | ;;; assoc.el ends here |