permsign

Function: permsign
Section: combinatorics
C-Name: permsign
Prototype: lG
Help: permsign(x): signature of the permutation x.
Doc: given a permutation $x$ on $n$ elements, return its signature.
 \bprog
 ? p = Vecsmall([3,1,4,2,5]);
 ? permsign(p)
 %2 = -1
 ? permsign(p^2)
 %3 = 1
 @eprog