FUNCTION: FreeMinus - difference of two elements of the free algebra

CALLING SEQUENCE:

FreeMinus(e_1, e_2)

FREE[FreeMinus](e_1, e_2)

PARAMETERS:

e_1, e_2 = any elements of the free algebra

SYNOPSIS:

• The FreeMinus function computes the difference of two elements of the free algebra. It corresponds to the usual operation `-` but the function normalizes the result, by essentially collecting coefficients.

• One can use instead the operator &~-.

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

EXAMPLES:

> with(FREE):
> a:=q + u/t*w[2,1,1]:
> b:=t - w[1,2,2]:
> FreeMinus(a, b);
 
                   u w[2, 1, 1]
                   ------------ + (q - t) w[] + w[1, 2, 2]
                         t
 
> a &~- a;
 
                                      0