1;;; soundex.el --- implement Soundex algorithm 2 3;; Copyright (C) 1993, 2001, 2002, 2003, 2004, 2005, 4;; 2006, 2007 Free Software Foundation, Inc. 5 6;; Author: Christian Plaunt <chris@bliss.berkeley.edu> 7;; Maintainer: FSF 8;; Keywords: matching 9;; Created: Sat May 15 14:48:18 1993 10 11;; This file is part of GNU Emacs. 12 13;; GNU Emacs is free software; you can redistribute it and/or modify 14;; it under the terms of the GNU General Public License as published by 15;; the Free Software Foundation; either version 2, or (at your option) 16;; any later version. 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 24;; along with GNU Emacs; see the file COPYING. If not, write to the 25;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, 26;; Boston, MA 02110-1301, USA. 27 28;;; Commentary: 29 30;; The Soundex algorithm maps English words into representations of 31;; how they sound. Words with vaguely similar sound map to the same string. 32 33;;; Code: 34 35(defvar soundex-alist 36 '((?B . "1") (?F . "1") (?P . "1") (?V . "1") 37 (?C . "2") (?G . "2") (?J . "2") (?K . "2") (?Q . "2") (?S . "2") 38 (?X . "2") (?Z . "2") (?D . "3") (?T . "3") (?L . "4") (?M . "5") 39 (?N . "5") (?R . "6")) 40 "Alist of chars-to-key-code for building Soundex keys.") 41 42(defun soundex (word) 43 "Return a Soundex key for WORD. 44Implemented as described in: 45Knuth, Donald E. \"The Art of Computer Programming, Vol. 3: Sorting 46and Searching\", Addison-Wesley (1973), pp. 391-392." 47 (let* ((word (upcase word)) (length (length word)) 48 (code (cdr (assq (aref word 0) soundex-alist))) 49 (key (substring word 0 1)) (index 1) (prev-code code)) 50 ;; once we have a four char key, we're done 51 (while (and (> 4 (length key)) (< index length)) 52 ;; look up the code for each letter in word at index 53 (setq code (cdr (assq (aref word index) soundex-alist)) 54 index (1+ index) 55 ;; append code to key unless the same codes belong to 56 ;; adjacent letters in the original string 57 key (concat key (if (or (null code) (string= code prev-code)) 58 () 59 code)) 60 prev-code code)) 61 ;; return a key that is 4 chars long and padded by "0"s if needed 62 (if (> 4 (length key)) 63 (substring (concat key "000") 0 4) 64 key))) 65 66;(defvar soundex-test 67; '("Euler" "Gauss" "Hilbert" "Knuth" "Lloyd" "Lukasiewicz" 68; "Ellery" "Ghosh" "Heilbronn" "Kant" "Ladd" "Lissajous") 69; "\n Knuth's names to demonstrate the Soundex algorithm.") 70; 71;(mapcar 'soundex soundex-test) 72;("E460" "G200" "H416" "K530" "L300" "L222" 73; "E460" "G200" "H416" "K530" "L300" "L222") 74 75(provide 'soundex) 76 77;;; arch-tag: b2615a98-feb7-430e-a717-171086738953 78;;; soundex.el ends here 79