FUNCTION: IsBnBar - test whether the argument is a signed permutation

CALLING SEQUENCE:

IsBnBar(expr)

TYP[IsBnBar](expr)

PARAMETERS:

expr = any expression

SYNOPSIS:

• The IsBnBar function tests whether expr is a signed permutation, that is a list of n distinct positive or negative integers, with distinct absolute values between 1 and n.

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

EXAMPLES:

> with(TYP):
> IsBnBar([-2, 1, 2]);
 
                                    false
 
> IsBnBar([-2, 3, -1]);
 
                                     true