FUNCTION: Rd2BnNca - calculate a product of generators

CALLING SEQUENCE:

Rd2BnNca(rd)

Rd2BnNca(rd, n)

BNA[Rd2BnNca](rd)

BNA[Rd2BnNca](rd, n)

PARAMETERS:

rd = any list denoting a decomposition

n = any positive integer

SYNOPSIS:

• The Rd2BnNca function calculates the product of the generators given by the decomposition rd (0 denotes the special generator). The product is taken in the Bn-nilCoxeter algebra.

• If rd is reduced then Rd2BnNca(rd)=BN['BnRd2Code'](rd), and 0 otherwise.

• When the second argument is not present, n is the smallest possible degree.

• Whenever there is a conflict between the function name Rd2BnNca and another name used in the same session, use the long form BNA['Rd2BnNca'].

EXAMPLES:

> with(BNA):
> Rd2BnNca([0,1,0,1], 5);
 
                                B[1, 3, 0, 0, 0]
 
> Rd2BnNca([0,1,0,1]);
 
                                     B[1, 3]
 
> Rd2BnNca([1,0,1,0,1]);
 
                                        0