FUNCTION: IssA - test whether the argument is an element of the Schur basis on a formal alphabet expression

CALLING SEQUENCE:

IssA(expr)

TYP[IssA](expr)

PARAMETERS:

expr = any expression

SYNOPSIS:

• The IssA function tests whether the argument expr is an element of the Schur basis, that is s[part](alphab) where part denotes a partition in non-increasing order and alphab is a valid formal alphabet expression.

• Allowed alphabet expressions are linear combinations of formal alphabets A1, A2, etc.

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

EXAMPLES:

> with(TYP):
> IssA( s[2,1,1](A1-A2) );
 
                                     true
 
> IssA( s[3,3,1](2/3*A3) );
 
                                     true