#!/usr/bin/ruby

func levenshtein(s, t) is cached {

    s.is_empty && return t.len;
    t.is_empty && return s.len;

    var s1 = s.slice(1);
    var t1 = t.slice(1);

    s[0] == t[0]
            ? __FUNC__(s1, t1)
            : (1 + [
                    __FUNC__(s1, t1),
                    __FUNC__(s,  t1),
                    __FUNC__(s1, t ),
                   ].min
              );
}

assert_eq(levenshtein(%c"kitten", %c"sitting"), 3);
assert_eq(levenshtein(%c"rosettacode", %c"raisethysword"), 8);
assert_eq(levenshtein(%G"J\x{332}o\x{332}s\x{332}e\x{301}\x{332}", %G"J\x{332}o\x{332}s\x{332}"), 1);

say "** Test passed!";