mirror of
https://git.savannah.gnu.org/git/emacs.git
synced 2024-12-16 09:50:25 +00:00
66 lines
2.4 KiB
EmacsLisp
66 lines
2.4 KiB
EmacsLisp
;;; soundex.el --- implement Soundex algorithm -*- lexical-binding: t -*-
|
|
|
|
;; Copyright (C) 1993, 2001-2020 Free Software Foundation, Inc.
|
|
|
|
;; Author: Christian Plaunt <chris@bliss.berkeley.edu>
|
|
;; Maintainer: emacs-devel@gnu.org
|
|
;; Keywords: matching
|
|
;; Created: Sat May 15 14:48:18 1993
|
|
|
|
;; This file is part of GNU Emacs.
|
|
|
|
;; GNU Emacs is free software: you can redistribute it and/or modify
|
|
;; it under the terms of the GNU General Public License as published by
|
|
;; the Free Software Foundation, either version 3 of the License, or
|
|
;; (at your option) any later version.
|
|
|
|
;; GNU Emacs is distributed in the hope that it will be useful,
|
|
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
;; GNU General Public License for more details.
|
|
|
|
;; You should have received a copy of the GNU General Public License
|
|
;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
|
|
|
|
;;; Commentary:
|
|
|
|
;; The Soundex algorithm maps English words into representations of
|
|
;; how they sound. Words with vaguely similar sound map to the same string.
|
|
|
|
;;; Code:
|
|
|
|
(defconst soundex-alist
|
|
'((?B . "1") (?F . "1") (?P . "1") (?V . "1")
|
|
(?C . "2") (?G . "2") (?J . "2") (?K . "2") (?Q . "2") (?S . "2")
|
|
(?X . "2") (?Z . "2") (?D . "3") (?T . "3") (?L . "4") (?M . "5")
|
|
(?N . "5") (?R . "6"))
|
|
"Alist of chars-to-key-code for building Soundex keys.")
|
|
|
|
(defun soundex (word)
|
|
"Return a Soundex key for WORD.
|
|
Implemented as described in:
|
|
Knuth, Donald E. \"The Art of Computer Programming, Vol. 3: Sorting
|
|
and Searching\", Addison-Wesley (1973), pp. 391-392."
|
|
(let* ((word (upcase word)) (length (length word))
|
|
(code (cdr (assq (aref word 0) soundex-alist)))
|
|
(key (substring word 0 1)) (index 1) (prev-code code))
|
|
;; once we have a four char key, we're done
|
|
(while (and (> 4 (length key)) (< index length))
|
|
;; look up the code for each letter in word at index
|
|
(setq code (cdr (assq (aref word index) soundex-alist))
|
|
index (1+ index)
|
|
;; append code to key unless the same codes belong to
|
|
;; adjacent letters in the original string
|
|
key (concat key (if (or (null code) (string= code prev-code))
|
|
()
|
|
code))
|
|
prev-code code))
|
|
;; return a key that is 4 chars long and padded by "0"s if needed
|
|
(if (> 4 (length key))
|
|
(substring (concat key "000") 0 4)
|
|
key)))
|
|
|
|
(provide 'soundex)
|
|
|
|
;;; soundex.el ends here
|