bc511a64f6
Most of this change is to boilerplate commentary such as license URLs. This change was prompted by ftp://ftp.gnu.org's going-away party, planned for November. Change these FTP URLs to https://ftp.gnu.org instead. Make similar changes for URLs to other organizations moving away from FTP. Also, change HTTP to HTTPS for URLs to gnu.org and fsf.org when this works, as this will further help defend against man-in-the-middle attacks (for this part I omitted the MS-DOS and MS-Windows sources and the test tarballs to keep the workload down). HTTPS is not fully working to lists.gnu.org so I left those URLs alone for now.
65 lines
2.4 KiB
EmacsLisp
65 lines
2.4 KiB
EmacsLisp
;;; soundex.el --- implement Soundex algorithm -*- lexical-binding: t -*-
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;; Copyright (C) 1993, 2001-2017 Free Software Foundation, Inc.
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;; Author: Christian Plaunt <chris@bliss.berkeley.edu>
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;; Maintainer: emacs-devel@gnu.org
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;; Keywords: matching
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;; Created: Sat May 15 14:48:18 1993
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
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;;; Commentary:
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;; The Soundex algorithm maps English words into representations of
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;; how they sound. Words with vaguely similar sound map to the same string.
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;;; Code:
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(defconst soundex-alist
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'((?B . "1") (?F . "1") (?P . "1") (?V . "1")
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(?C . "2") (?G . "2") (?J . "2") (?K . "2") (?Q . "2") (?S . "2")
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(?X . "2") (?Z . "2") (?D . "3") (?T . "3") (?L . "4") (?M . "5")
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(?N . "5") (?R . "6"))
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"Alist of chars-to-key-code for building Soundex keys.")
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(defun soundex (word)
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"Return a Soundex key for WORD.
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Implemented as described in:
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Knuth, Donald E. \"The Art of Computer Programming, Vol. 3: Sorting
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and Searching\", Addison-Wesley (1973), pp. 391-392."
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(let* ((word (upcase word)) (length (length word))
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(code (cdr (assq (aref word 0) soundex-alist)))
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(key (substring word 0 1)) (index 1) (prev-code code))
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;; once we have a four char key, we're done
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(while (and (> 4 (length key)) (< index length))
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;; look up the code for each letter in word at index
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(setq code (cdr (assq (aref word index) soundex-alist))
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index (1+ index)
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;; append code to key unless the same codes belong to
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;; adjacent letters in the original string
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key (concat key (if (or (null code) (string= code prev-code))
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()
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code))
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prev-code code))
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;; return a key that is 4 chars long and padded by "0"s if needed
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(if (> 4 (length key))
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(substring (concat key "000") 0 4)
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key)))
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(provide 'soundex)
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;;; soundex.el ends here
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