FUNCTION: FactorPerm - test whether a permutation factorizes into a direct product

CALLING SEQUENCE:

FactorPerm(perm, 'l')

SG[FactorPerm](perm, 'l')

PARAMETERS:

perm = any list denoting a permutation

SYNOPSIS:

• Given a permutation perm in Sn, the FactorPerm function tests whether perm belongs to a Young sub-group Si x Sj. If it factorizes, the second formal parameter 'l' is set to the minimal length of a left block.

• Whenever there is a conflict between the function name FactorPerm and another name used in the same session, use the long form SG['FactorPerm'].

EXAMPLES:

> with(SG):
> FactorPerm([3,1,2,5,4,7,6], 'l');
 
                                      true
> l;
 
                                       3