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Marc A. Lehmann > String-Similarity-1.04 > String::Similarity



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String::Similarity - calculate the similarity of two strings


 use String::Similarity;

 $similarity = similarity $string1, $string2;
 $similarity = similarity $string1, $string2, $limit;


$factor = similarity $string1, $string2, [$limit]

The similarity-function calculates the similarity index of its two arguments. A value of 0 means that the strings are entirely different. A value of 1 means that the strings are identical. Everything else lies between 0 and 1 and describes the amount of similarity between the strings.

It roughly works by looking at the smallest number of edits to change one string into the other.

You can add an optional argument $limit (default 0) that gives the minimum similarity the two strings must satisfy. similarity stops analyzing the string as soon as the result drops below the given limit, in which case the result will be invalid but lower than the given $limit. You can use this to speed up the common case of searching for the most similar string from a set by specifing the maximum similarity found so far.


 The basic algorithm is described in:
 "An O(ND) Difference Algorithm and its Variations", Eugene Myers,
 Algorithmica Vol. 1 No. 2, 1986, pp. 251-266;
 see especially section 4.2, which describes the variation used below.

 The basic algorithm was independently discovered as described in:
 "Algorithms for Approximate String Matching", E. Ukkonen,
 Information and Control Vol. 64, 1985, pp. 100-118.


 Marc Lehmann <>

 (the underlying fstrcmp function was taken from gnu diffutils and
 modified by Peter Miller <> and Marc Lehmann
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