FUNCTION: BnMat2Bar - calculate the signed permutation from a given permutation matrix

CALLING SEQUENCE:

BnMat2Bar(mat)

BN[BnMat2Bar](mat)

PARAMETERS:

mat = any signed permutation matrix

SYNOPSIS:

• The BnMat2Bar function calculates the signed permutation corresponding to a given permutation matrix. 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 BnMat2Bar and another name used in the same session, use the long form BN['BnMat2Bar'].

EXAMPLES:

> with(BN):
> BnBar2Mat([-3, 2, -1]);
 
                                [  0  0  -1 ]
                                [           ]
                                [  0  1   0 ]
                                [           ]
                                [ -1  0   0 ]
 
> BnMat2Bar( BnBar2Mat([-3, 2, -1]) );
 
                                 [-3, 2, -1]