| 1 | ;; -*- Mode: Emacs-Lisp -*- |
| 2 | ;; sc-alist.el -- Version 1.0 (used to be baw-alist.el) |
| 3 | |
| 4 | ;; association list utilities providing insertion, deletion, sorting |
| 5 | ;; fetching off key-value pairs in association lists. |
| 6 | |
| 7 | ;; ========== Disclaimer ========== |
| 8 | ;; This software is distributed in the hope that it will be useful, |
| 9 | ;; but WITHOUT ANY WARRANTY. No author or distributor accepts |
| 10 | ;; responsibility to anyone for the consequences of using it or for |
| 11 | ;; whether it serves any particular purpose or works at all, unless he |
| 12 | ;; says so in writing. |
| 13 | |
| 14 | ;; This software was written as part of the supercite author's |
| 15 | ;; official duty as an employee of the United States Government and is |
| 16 | ;; thus in the public domain. You are free to use that particular |
| 17 | ;; software as you wish, but WITHOUT ANY WARRANTY WHATSOEVER. It |
| 18 | ;; would be nice, though if when you use any of this code, you give |
| 19 | ;; due credit to the author. |
| 20 | |
| 21 | ;; ========== Author (unless otherwise stated) ======================== |
| 22 | ;; NAME: Barry A. Warsaw USMAIL: Century Computing, Inc. |
| 23 | ;; TELE: (301) 593-3330 1014 West Street |
| 24 | ;; INET: bwarsaw@cen.com Laurel, Md 20707 |
| 25 | ;; UUCP: uunet!cen.com!bwarsaw |
| 26 | ;; |
| 27 | (provide 'sc-alist) |
| 28 | |
| 29 | |
| 30 | (defun asort (alist-symbol key) |
| 31 | "Move a specified key-value pair to the head of an alist. |
| 32 | The alist is referenced by ALIST-SYMBOL. Key-value pair to move to |
| 33 | head is one matching KEY. Returns the sorted list and doesn't affect |
| 34 | the order of any other key-value pair. Side effect sets alist to new |
| 35 | sorted list." |
| 36 | (set alist-symbol |
| 37 | (sort (copy-alist (eval alist-symbol)) |
| 38 | (function (lambda (a b) (equal (car a) key)))))) |
| 39 | |
| 40 | |
| 41 | (defun aelement (key value) |
| 42 | "Makes a list of a cons cell containing car of KEY and cdr of VALUE. |
| 43 | The returned list is suitable as an element of an alist." |
| 44 | (list (cons key value))) |
| 45 | |
| 46 | |
| 47 | (defun aheadsym (alist) |
| 48 | "Return the key symbol at the head of ALIST." |
| 49 | (car (car alist))) |
| 50 | |
| 51 | |
| 52 | (defun anot-head-p (alist key) |
| 53 | "Find out if a specified key-value pair is not at the head of an alist. |
| 54 | The alist to check is specified by ALIST and the key-value pair is the |
| 55 | one matching the supplied KEY. Returns nil if ALIST is nil, or if |
| 56 | key-value pair is at the head of the alist. Returns t if key-value |
| 57 | pair is not at the head of alist. ALIST is not altered." |
| 58 | (not (equal (aheadsym alist) key))) |
| 59 | |
| 60 | |
| 61 | (defun aput (alist-symbol key &optional value) |
| 62 | "Inserts a key-value pair into an alist. |
| 63 | The alist is referenced by ALIST-SYMBOL. The key-value pair is made |
| 64 | from KEY and optionally, VALUE. Returns the altered alist or nil if |
| 65 | ALIST is nil. |
| 66 | |
| 67 | If the key-value pair referenced by KEY can be found in the alist, and |
| 68 | VALUE is supplied non-nil, then the value of KEY will be set to VALUE. |
| 69 | If VALUE is not supplied, or is nil, the key-value pair will not be |
| 70 | modified, but will be moved to the head of the alist. If the key-value |
| 71 | pair cannot be found in the alist, it will be inserted into the head |
| 72 | of the alist (with value nil if VALUE is nil or not supplied)." |
| 73 | (let ((elem (aelement key value)) |
| 74 | alist) |
| 75 | (asort alist-symbol key) |
| 76 | (setq alist (eval alist-symbol)) |
| 77 | (cond ((null alist) (set alist-symbol elem)) |
| 78 | ((anot-head-p alist key) (set alist-symbol (nconc elem alist))) |
| 79 | (value (setcar alist (car elem))) |
| 80 | (t alist)))) |
| 81 | |
| 82 | |
| 83 | (defun adelete (alist-symbol key) |
| 84 | "Delete a key-value pair from the alist. |
| 85 | Alist is referenced by ALIST-SYMBOL and the key-value pair to remove |
| 86 | is pair matching KEY. Returns the altered alist." |
| 87 | (asort alist-symbol key) |
| 88 | (let ((alist (eval alist-symbol))) |
| 89 | (cond ((null alist) nil) |
| 90 | ((anot-head-p alist key) alist) |
| 91 | (t (set alist-symbol (cdr alist)))))) |
| 92 | |
| 93 | |
| 94 | (defun aget (alist key &optional keynil-p) |
| 95 | "Returns the value in ALIST that is associated with KEY. |
| 96 | Optional KEYNIL-P describes what to do if the value associated with |
| 97 | KEY is nil. If KEYNIL-P is not supplied or is nil, and the value is |
| 98 | nil, then KEY is returned. If KEYNIL-P is non-nil, then nil would be |
| 99 | returned. |
| 100 | |
| 101 | If no key-value pair matching KEY could be found in ALIST, or ALIST is |
| 102 | nil then nil is returned. ALIST is not altered." |
| 103 | (let ((copy (copy-alist alist))) |
| 104 | (cond ((null alist) nil) |
| 105 | ((progn (asort 'copy key) |
| 106 | (anot-head-p copy key)) nil) |
| 107 | ((cdr (car copy))) |
| 108 | (keynil-p nil) |
| 109 | ((car (car copy))) |
| 110 | (t nil)))) |
| 111 | |
| 112 | |
| 113 | (defun amake (alist-symbol keylist &optional valuelist) |
| 114 | "Make an association list. |
| 115 | The association list is attached to the alist referenced by |
| 116 | ALIST-SYMBOL. Each element in the KEYLIST becomes a key and is |
| 117 | associated with the value in VALUELIST with the same index. If |
| 118 | VALUELIST is not supplied or is nil, then each key in KEYLIST is |
| 119 | associated with nil. |
| 120 | |
| 121 | KEYLIST and VALUELIST should have the same number of elements, but |
| 122 | this isn't enforced. If VALUELIST is smaller than KEYLIST, remaining |
| 123 | keys are associated with nil. If VALUELIST is larger than KEYLIST, |
| 124 | extra values are ignored. Returns the created alist." |
| 125 | (let ((keycar (car keylist)) |
| 126 | (keycdr (cdr keylist)) |
| 127 | (valcar (car valuelist)) |
| 128 | (valcdr (cdr valuelist))) |
| 129 | (cond ((null keycdr) |
| 130 | (aput alist-symbol keycar valcar)) |
| 131 | (t |
| 132 | (amake alist-symbol keycdr valcdr) |
| 133 | (aput alist-symbol keycar valcar)))) |
| 134 | (eval alist-symbol)) |