Paul Rubin wrote: > John Machin <[EMAIL PROTECTED]> writes: ... > > 3. Of what practical use (or even esoteric academic interest) is the > > parity of the number of interchanges? > > It is of considerable interest in combinatorics. The group of even > permutations on N elements is called the alternating group A(N). > It's an order-2 subgroup of the symmetric group S(N) which is the > group of all the permutations on N elements. The odd permutations > are of course a coset of A(N).
It's also used in linear algebra, as part of the definition of the determinant. -- http://mail.python.org/mailman/listinfo/python-list