The HammingDistance(s,t) command returns an integer measure of the distance between the two strings s and t.

The Hamming distance between two strings s and t, of equal length, is the number of character positions where they differ. If strings s and t have respective lengths m and n where, without loss of generality, , then the generalized Hamming distance between s and t is defined to be (m - n) + HammingDistance( s[ 1 .. n ], t ). The HammingDistance procedure computes this generalized metric.

For a different notion of the distance between two strings, see StringTools[Levenshtein].