permutation

Usage:
    <permutation n x[i1]x[i2]..x[in] p
computes the permutation matrix which expresses
    i1..in
as a
permutation of
    1..n.
Parameters:
            n = number of letters permuted
            x[i1]x[i2]..x[in] = the permutation, as a list in order
                                    of the variables x[1]x[2]..x[n]
Output values:
            p = n x n matrix expressing the permutation.