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b035a678 | 1 | ;;; soundex.el --- implement Soundex algorithm |
7d95a391 RS |
2 | |
3 | ;; Copyright (C) 1993 Free Software Foundation, Inc. | |
4 | ||
5 | ;; Author: Christian Plaunt <chris@bliss.berkeley.edu> | |
f1180544 | 6 | ;; Maintainer: FSF |
7d95a391 RS |
7 | ;; Keywords: matching |
8 | ;; Created: Sat May 15 14:48:18 1993 | |
9 | ||
10 | ;; This file is part of GNU Emacs. | |
11 | ||
12 | ;; GNU Emacs is free software; you can redistribute it and/or modify | |
13 | ;; it under the terms of the GNU General Public License as published by | |
14 | ;; the Free Software Foundation; either version 2, or (at your option) | |
15 | ;; any later version. | |
16 | ||
17 | ;; GNU Emacs is distributed in the hope that it will be useful, | |
18 | ;; but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | ;; GNU General Public License for more details. | |
21 | ||
22 | ;; You should have received a copy of the GNU General Public License | |
b578f267 EN |
23 | ;; along with GNU Emacs; see the file COPYING. If not, write to the |
24 | ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330, | |
25 | ;; Boston, MA 02111-1307, USA. | |
7d95a391 RS |
26 | |
27 | ;;; Commentary: | |
28 | ||
29 | ;; The Soundex algorithm maps English words into representations of | |
30 | ;; how they sound. Words with vaguely similar sound map to the same string. | |
31 | ||
55535639 | 32 | ;;; Code: |
7d95a391 | 33 | |
c1558605 | 34 | (defvar soundex-alist |
c0b54990 | 35 | '((?B . "1") (?F . "1") (?P . "1") (?V . "1") |
c1558605 RS |
36 | (?C . "2") (?G . "2") (?J . "2") (?K . "2") (?Q . "2") (?S . "2") |
37 | (?X . "2") (?Z . "2") (?D . "3") (?T . "3") (?L . "4") (?M . "5") | |
38 | (?N . "5") (?R . "6")) | |
39 | "Alist of chars-to-key-code for building Soundex keys.") | |
40 | ||
7d95a391 RS |
41 | (defun soundex (word) |
42 | "Return a Soundex key for WORD. | |
43 | Implemented as described in: | |
44 | Knuth, Donald E. \"The Art of Computer Programming, Vol. 3: Sorting | |
45 | and Searching\", Addison-Wesley (1973), pp. 391-392." | |
46 | (let* ((word (upcase word)) (length (length word)) | |
47 | (code (cdr (assq (aref word 0) soundex-alist))) | |
48 | (key (substring word 0 1)) (index 1) (prev-code code)) | |
c0b54990 | 49 | ;; once we have a four char key, we're done |
7d95a391 RS |
50 | (while (and (> 4 (length key)) (< index length)) |
51 | ;; look up the code for each letter in word at index | |
52 | (setq code (cdr (assq (aref word index) soundex-alist)) | |
53 | index (1+ index) | |
54 | ;; append code to key unless the same codes belong to | |
55 | ;; adjacent letters in the original string | |
56 | key (concat key (if (or (null code) (string= code prev-code)) | |
57 | () | |
58 | code)) | |
59 | prev-code code)) | |
60 | ;; return a key that is 4 chars long and padded by "0"s if needed | |
61 | (if (> 4 (length key)) | |
62 | (substring (concat key "000") 0 4) | |
63 | key))) | |
64 | ||
7d95a391 RS |
65 | ;(defvar soundex-test |
66 | ; '("Euler" "Gauss" "Hilbert" "Knuth" "Lloyd" "Lukasiewicz" | |
67 | ; "Ellery" "Ghosh" "Heilbronn" "Kant" "Ladd" "Lissajous") | |
68 | ; "\n Knuth's names to demonstrate the Soundex algorithm.") | |
69 | ; | |
70 | ;(mapcar 'soundex soundex-test) | |
71 | ;("E460" "G200" "H416" "K530" "L300" "L222" | |
72 | ; "E460" "G200" "H416" "K530" "L300" "L222") | |
73 | ||
896546cd RS |
74 | (provide 'soundex) |
75 | ||
ab5796a9 | 76 | ;;; arch-tag: b2615a98-feb7-430e-a717-171086738953 |
55535639 | 77 | ;;; soundex.el ends here |