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1 | ;;; assoc.el --- insert/delete/sort functions on association lists |
2 | ||
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3 | ;; Copyright (C) 1996 Free Software Foundation, Inc. |
4 | ||
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5 | ;; Author: Barry A. Warsaw <bwarsaw@cen.com> |
6 | ;; Keywords: extensions | |
7 | ||
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8 | ;; This file is part of GNU Emacs. |
9 | ||
10 | ;; GNU Emacs is free software; you can redistribute it and/or modify | |
11 | ;; it under the terms of the GNU General Public License as published by | |
12 | ;; the Free Software Foundation; either version 2, or (at your option) | |
13 | ;; any later version. | |
14 | ||
15 | ;; GNU Emacs is distributed in the hope that it will be useful, | |
16 | ;; but WITHOUT ANY WARRANTY; without even the implied warranty of | |
17 | ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
18 | ;; GNU General Public License for more details. | |
19 | ||
20 | ;; You should have received a copy of the GNU General Public License | |
21 | ;; along with GNU Emacs; see the file COPYING. If not, write to the | |
22 | ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330, | |
23 | ;; Boston, MA 02111-1307, USA. | |
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24 | |
25 | ;;; Commentary: | |
26 | ||
27 | ;; Association list utilities providing insertion, deletion, sorting | |
28 | ;; fetching off key-value pairs in association lists. | |
29 | ||
30 | ;;; Code: | |
31 | ||
6476a5fa | 32 | (defun asort (alist-symbol key) |
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33 | "Move a specified key-value pair to the head of an alist. |
34 | The alist is referenced by ALIST-SYMBOL. Key-value pair to move to | |
35 | head is one matching KEY. Returns the sorted list and doesn't affect | |
36 | the order of any other key-value pair. Side effect sets alist to new | |
37 | sorted list." | |
38 | (set alist-symbol | |
39 | (sort (copy-alist (eval alist-symbol)) | |
40 | (function (lambda (a b) (equal (car a) key)))))) | |
41 | ||
42 | ||
43 | (defun aelement (key value) | |
44 | "Makes a list of a cons cell containing car of KEY and cdr of VALUE. | |
45 | The returned list is suitable as an element of an alist." | |
46 | (list (cons key value))) | |
47 | ||
48 | ||
49 | (defun aheadsym (alist) | |
50 | "Return the key symbol at the head of ALIST." | |
51 | (car (car alist))) | |
52 | ||
53 | ||
54 | (defun anot-head-p (alist key) | |
55 | "Find out if a specified key-value pair is not at the head of an alist. | |
56 | The alist to check is specified by ALIST and the key-value pair is the | |
57 | one matching the supplied KEY. Returns nil if ALIST is nil, or if | |
58 | key-value pair is at the head of the alist. Returns t if key-value | |
59 | pair is not at the head of alist. ALIST is not altered." | |
60 | (not (equal (aheadsym alist) key))) | |
61 | ||
62 | ||
63 | (defun aput (alist-symbol key &optional value) | |
64 | "Inserts a key-value pair into an alist. | |
65 | The alist is referenced by ALIST-SYMBOL. The key-value pair is made | |
2af4b890 | 66 | from KEY and optionally, VALUE. Returns the altered alist or nil if |
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67 | ALIST is nil. |
68 | ||
69 | If the key-value pair referenced by KEY can be found in the alist, and | |
70 | VALUE is supplied non-nil, then the value of KEY will be set to VALUE. | |
71 | If VALUE is not supplied, or is nil, the key-value pair will not be | |
72 | modified, but will be moved to the head of the alist. If the key-value | |
73 | pair cannot be found in the alist, it will be inserted into the head | |
74 | of the alist (with value nil if VALUE is nil or not supplied)." | |
75 | (let ((elem (aelement key value)) | |
76 | alist) | |
77 | (asort alist-symbol key) | |
78 | (setq alist (eval alist-symbol)) | |
79 | (cond ((null alist) (set alist-symbol elem)) | |
80 | ((anot-head-p alist key) (set alist-symbol (nconc elem alist))) | |
81 | (value (setcar alist (car elem))) | |
82 | (t alist)))) | |
83 | ||
84 | ||
85 | (defun adelete (alist-symbol key) | |
86 | "Delete a key-value pair from the alist. | |
87 | Alist is referenced by ALIST-SYMBOL and the key-value pair to remove | |
88 | is pair matching KEY. Returns the altered alist." | |
89 | (asort alist-symbol key) | |
90 | (let ((alist (eval alist-symbol))) | |
91 | (cond ((null alist) nil) | |
92 | ((anot-head-p alist key) alist) | |
93 | (t (set alist-symbol (cdr alist)))))) | |
94 | ||
95 | ||
96 | (defun aget (alist key &optional keynil-p) | |
97 | "Returns the value in ALIST that is associated with KEY. | |
98 | Optional KEYNIL-P describes what to do if the value associated with | |
99 | KEY is nil. If KEYNIL-P is not supplied or is nil, and the value is | |
100 | nil, then KEY is returned. If KEYNIL-P is non-nil, then nil would be | |
101 | returned. | |
102 | ||
103 | If no key-value pair matching KEY could be found in ALIST, or ALIST is | |
104 | nil then nil is returned. ALIST is not altered." | |
105 | (let ((copy (copy-alist alist))) | |
106 | (cond ((null alist) nil) | |
107 | ((progn (asort 'copy key) | |
108 | (anot-head-p copy key)) nil) | |
109 | ((cdr (car copy))) | |
110 | (keynil-p nil) | |
111 | ((car (car copy))) | |
112 | (t nil)))) | |
113 | ||
114 | ||
115 | (defun amake (alist-symbol keylist &optional valuelist) | |
116 | "Make an association list. | |
117 | The association list is attached to the alist referenced by | |
118 | ALIST-SYMBOL. Each element in the KEYLIST becomes a key and is | |
119 | associated with the value in VALUELIST with the same index. If | |
120 | VALUELIST is not supplied or is nil, then each key in KEYLIST is | |
121 | associated with nil. | |
122 | ||
123 | KEYLIST and VALUELIST should have the same number of elements, but | |
124 | this isn't enforced. If VALUELIST is smaller than KEYLIST, remaining | |
125 | keys are associated with nil. If VALUELIST is larger than KEYLIST, | |
126 | extra values are ignored. Returns the created alist." | |
127 | (let ((keycar (car keylist)) | |
128 | (keycdr (cdr keylist)) | |
129 | (valcar (car valuelist)) | |
130 | (valcdr (cdr valuelist))) | |
131 | (cond ((null keycdr) | |
132 | (aput alist-symbol keycar valcar)) | |
133 | (t | |
134 | (amake alist-symbol keycdr valcdr) | |
135 | (aput alist-symbol keycar valcar)))) | |
136 | (eval alist-symbol)) | |
137 | ||
138 | (provide 'assoc) | |
139 | ||
140 | ;;; assoc.el ends here |