Alignment

func align(s, t) {
    s.chars!.prepend!('^')
    t.chars!.prepend!('^')

    var A = []
    {|i| A[i][0]{@|<d s t>} = (i, s.slice(1).first(i).join, '~' * i) } << ^s
    {|i| A[0][i]{@|<d s t>} = (i, '-' * i, t.slice(1).first(i).join) } << ^t

    for i (1 .. s.end) {
      for j (1 .. t.end) {
        if (s[i] != t[j]) {
          A[i][j]{:d} = 1+(
            var min = Math.min(A[i-1][j]{:d}, A[i][j-1]{:d}, A[i-1][j-1]{:d})
          )
          A[i][j]{@|<s t>} = (A[i-1][j]{:d} == min
              ? [A[i-1][j]{:s}+s[i], A[i-1][j]{:t}+'-']
              : (A[i][j-1]{:d} == min
              ? [A[i][j-1]{:s}+'-', A[i][j-1]{:t}+t[j]]
              : [A[i-1][j-1]{:s}+s[i], A[i-1][j-1]{:t}+t[j]]))...
        }
        else {
          A[i][j]{@|<d s t>} = (
              A[i-1][j-1]{:d},
              A[i-1][j-1]{:s}+s[i],
              A[i-1][j-1]{:t}+t[j],
          )
        }
      }
    }
    return [A[-1][-1]{@|<s t>}]
}

align("rosettacode", "raisethysword").each { .say }

Output:

ro-settac-o-de
raisethysword-