The IsPermutation(s) command returns the value true if the string s is a permutation of its support, and returns the value false otherwise. A string is a permutation if, and only if, each character in the string occurs exactly once.

Note that, since there are only  distinct characters (byte values), the Pigeon-Hole Principle implies that no string permutation can exceed  characters in length.

If s is the empty string, the command returns true.