# Difference between revisions of "Soundex Matching"

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== Solution == | == Solution == | ||

− | + | Use the soundex module below: | |

− | + | ||

− | Use the soundex | + | |

<code> | <code> | ||

− | > | + | > soundex:soundex("Smith"). |

"S530" | "S530" | ||

− | > | + | > soundex:soundex("Smyth"). |

"S530" | "S530" | ||

</code> | </code> | ||

− | + | Soundex is a string hash historically used by the US Census for indexing surnames by a function of what they "sound" like, rather than their precise spelling. Further general information on Soundex is available at http://www.archives.gov/research_room/genealogy/census/soundex.html. | |

− | + | ||

− | + | ||

− | + | ||

− | + | ||

− | + | ||

− | + | ||

− | + | == Implementation == | |

<code> | <code> | ||

− | + | -module(soundex). | |

− | + | ||

− | + | ||

+ | -export([soundex/1]). | ||

− | + | soundex([]) -> []; | |

− | + | %% | |

− | < | + | soundex([First|T]) -> |

− | > ( | + | pad([First|[num(X) || X <- strip(httpd_util:to_upper(T))]]). |

− | + | ||

− | > ( | + | strip(String) -> strip(String, []). |

− | + | strip([$A|T], Acc) -> strip(T, Acc); | |

− | + | strip([$E|T], Acc) -> strip(T, Acc); | |

+ | strip([$H|T], Acc) -> strip(T, Acc); | ||

+ | strip([$I|T], Acc) -> strip(T, Acc); | ||

+ | strip([$O|T], Acc) -> strip(T, Acc); | ||

+ | strip([$U|T], Acc) -> strip(T, Acc); | ||

+ | strip([$W|T], Acc) -> strip(T, Acc); | ||

+ | strip([$Y|T], Acc) -> strip(T, Acc); | ||

+ | strip([32|T], Acc) -> strip(T, Acc); | ||

+ | strip([C|T], Acc) -> strip(T, [C|Acc]); | ||

+ | strip([], Acc) -> lists:reverse(Acc). | ||

+ | num($B) -> $1; num($F) -> $1; num($P) -> $1; num($V) -> $1; | ||

+ | num($C) -> $2; num($G) -> $2; num($J) -> $2; num($K) -> $2; | ||

+ | num($Q) -> $2; num($S) -> $2; num($X) -> $2; num($Z) -> $2; | ||

+ | num($D) -> $3; num($T) -> $3; | ||

+ | num($L) -> $4; | ||

+ | num($M) -> $5; num($N) -> $5; | ||

+ | num($R) -> $6. | ||

+ | dedup(String) -> dedup(String, []). | ||

+ | dedup([X,X|T], Acc) -> dedup([X|T], Acc); | ||

+ | dedup([C|T], Acc) -> dedup(T, [C|Acc]); | ||

+ | dedup([], Acc) -> lists:reverse(Acc). | ||

− | + | pad([A,B,C,D]) -> [A,B,C,D]; | |

+ | pad([A,B,C]) -> [A,B,C,$0]; | ||

+ | pad([A,B]) -> [A,B,$0,$0]; | ||

+ | pad([A]) -> [A,$0,$0,$0]; | ||

+ | pad([]) -> [$0,$0,$0,$0]. | ||

+ | </code> | ||

− | [[Category:CookBook]] | + | [[Category:CookBook]][[Category:StringRecipes]] |

## Revision as of 12:52, 23 November 2006

## Problem

You want to generate Soundex hashes of surnames, for doing "sounds-like" indexing databases, or retrieving information from the US Census records and similar pre-existing databases.

## Solution

Use the soundex module below:

> soundex:soundex("Smith"). "S530" > soundex:soundex("Smyth"). "S530"

Soundex is a string hash historically used by the US Census for indexing surnames by a function of what they "sound" like, rather than their precise spelling. Further general information on Soundex is available at http://www.archives.gov/research_room/genealogy/census/soundex.html.

## Implementation

-module(soundex). -export([soundex/1]). soundex([]) -> []; %% soundex([First|T]) -> pad([First|[num(X) || X <- strip(httpd_util:to_upper(T))]]). strip(String) -> strip(String, []). strip([$A|T], Acc) -> strip(T, Acc); strip([$E|T], Acc) -> strip(T, Acc); strip([$H|T], Acc) -> strip(T, Acc); strip([$I|T], Acc) -> strip(T, Acc); strip([$O|T], Acc) -> strip(T, Acc); strip([$U|T], Acc) -> strip(T, Acc); strip([$W|T], Acc) -> strip(T, Acc); strip([$Y|T], Acc) -> strip(T, Acc); strip([32|T], Acc) -> strip(T, Acc); strip([C|T], Acc) -> strip(T, [C|Acc]); strip([], Acc) -> lists:reverse(Acc). num($B) -> $1; num($F) -> $1; num($P) -> $1; num($V) -> $1; num($C) -> $2; num($G) -> $2; num($J) -> $2; num($K) -> $2; num($Q) -> $2; num($S) -> $2; num($X) -> $2; num($Z) -> $2; num($D) -> $3; num($T) -> $3; num($L) -> $4; num($M) -> $5; num($N) -> $5; num($R) -> $6. dedup(String) -> dedup(String, []). dedup([X,X|T], Acc) -> dedup([X|T], Acc); dedup([C|T], Acc) -> dedup(T, [C|Acc]); dedup([], Acc) -> lists:reverse(Acc). pad([A,B,C,D]) -> [A,B,C,D]; pad([A,B,C]) -> [A,B,C,$0]; pad([A,B]) -> [A,B,$0,$0]; pad([A]) -> [A,$0,$0,$0]; pad([]) -> [$0,$0,$0,$0].