FUNCTION: BnBar2Mat - signed permutation matrix from a signed permutation

CALLING SEQUENCE:

BnBar2Mat(bar)

BN[BnBar2Mat](bar)

PARAMETERS:

bar = any list denoting a signed permutation

SYNOPSIS:

• The BnBar2Mat function calculates the matrix corresponding to the signed permutation bar. This matrix has entries either 1 or -1 in position (i, abs(bar[i])) and 0 otherwise. The sign of the entry in the i-th row, is the sign of bar[i].

• Whenever there is a conflict between the function name BnBar2Mat and another name used in the same session, use the long form BN['BnBar2Mat'].

EXAMPLES:

> with(BN):
> BnBar2Mat([-3, 2, -1]);
 
                                [  0  0  -1 ]
                                [           ]
                                [  0  1   0 ]
                                [           ]
                                [ -1  0   0 ]