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b035a678 | 1 | ;;; soundex.el --- implement Soundex algorithm |
7d95a391 | 2 | |
c90f2757 | 3 | ;; Copyright (C) 1993, 2001, 2002, 2003, 2004, 2005, |
114f9c96 | 4 | ;; 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc. |
7d95a391 RS |
5 | |
6 | ;; Author: Christian Plaunt <chris@bliss.berkeley.edu> | |
f1180544 | 7 | ;; Maintainer: FSF |
7d95a391 RS |
8 | ;; Keywords: matching |
9 | ;; Created: Sat May 15 14:48:18 1993 | |
10 | ||
11 | ;; This file is part of GNU Emacs. | |
12 | ||
eb3fa2cf | 13 | ;; GNU Emacs is free software: you can redistribute it and/or modify |
7d95a391 | 14 | ;; it under the terms of the GNU General Public License as published by |
eb3fa2cf GM |
15 | ;; the Free Software Foundation, either version 3 of the License, or |
16 | ;; (at your option) any later version. | |
7d95a391 RS |
17 | |
18 | ;; GNU Emacs is distributed in the hope that it will be useful, | |
19 | ;; but WITHOUT ANY WARRANTY; without even the implied warranty of | |
20 | ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
21 | ;; GNU General Public License for more details. | |
22 | ||
23 | ;; You should have received a copy of the GNU General Public License | |
eb3fa2cf | 24 | ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. |
7d95a391 RS |
25 | |
26 | ;;; Commentary: | |
27 | ||
28 | ;; The Soundex algorithm maps English words into representations of | |
29 | ;; how they sound. Words with vaguely similar sound map to the same string. | |
30 | ||
55535639 | 31 | ;;; Code: |
7d95a391 | 32 | |
c1558605 | 33 | (defvar soundex-alist |
c0b54990 | 34 | '((?B . "1") (?F . "1") (?P . "1") (?V . "1") |
c1558605 RS |
35 | (?C . "2") (?G . "2") (?J . "2") (?K . "2") (?Q . "2") (?S . "2") |
36 | (?X . "2") (?Z . "2") (?D . "3") (?T . "3") (?L . "4") (?M . "5") | |
37 | (?N . "5") (?R . "6")) | |
38 | "Alist of chars-to-key-code for building Soundex keys.") | |
39 | ||
7d95a391 RS |
40 | (defun soundex (word) |
41 | "Return a Soundex key for WORD. | |
42 | Implemented as described in: | |
43 | Knuth, Donald E. \"The Art of Computer Programming, Vol. 3: Sorting | |
44 | and Searching\", Addison-Wesley (1973), pp. 391-392." | |
45 | (let* ((word (upcase word)) (length (length word)) | |
46 | (code (cdr (assq (aref word 0) soundex-alist))) | |
47 | (key (substring word 0 1)) (index 1) (prev-code code)) | |
c0b54990 | 48 | ;; once we have a four char key, we're done |
7d95a391 RS |
49 | (while (and (> 4 (length key)) (< index length)) |
50 | ;; look up the code for each letter in word at index | |
51 | (setq code (cdr (assq (aref word index) soundex-alist)) | |
52 | index (1+ index) | |
53 | ;; append code to key unless the same codes belong to | |
54 | ;; adjacent letters in the original string | |
55 | key (concat key (if (or (null code) (string= code prev-code)) | |
56 | () | |
57 | code)) | |
58 | prev-code code)) | |
59 | ;; return a key that is 4 chars long and padded by "0"s if needed | |
60 | (if (> 4 (length key)) | |
61 | (substring (concat key "000") 0 4) | |
62 | key))) | |
63 | ||
7d95a391 RS |
64 | ;(defvar soundex-test |
65 | ; '("Euler" "Gauss" "Hilbert" "Knuth" "Lloyd" "Lukasiewicz" | |
66 | ; "Ellery" "Ghosh" "Heilbronn" "Kant" "Ladd" "Lissajous") | |
67 | ; "\n Knuth's names to demonstrate the Soundex algorithm.") | |
68 | ; | |
69 | ;(mapcar 'soundex soundex-test) | |
70 | ;("E460" "G200" "H416" "K530" "L300" "L222" | |
71 | ; "E460" "G200" "H416" "K530" "L300" "L222") | |
72 | ||
896546cd RS |
73 | (provide 'soundex) |
74 | ||
cbee283d | 75 | ;; arch-tag: b2615a98-feb7-430e-a717-171086738953 |
55535639 | 76 | ;;; soundex.el ends here |