fetch matrix M result matrix N [1]

Create a new matrix, N over the current ring which is essentially the matrix M: each variable in the base ring of M which also occurs in the current ring is left unchanged, and each variable which doesn't occur is set to zero by default (or one, if the optional third argument is given).

This command is useful for changing monomial orders, inclusion of one ring in another, or projection of one ring to another.

The following example ``fetch''s the matrix m from the ring R to the ring S.

%  type m     ; the base ring of m is R.
; a   a2    
; b+c ab+d2 

%  ; make sure the current ring is S, which has vars a,b,c
%  setring S  

%  fetch m n

%  type n     ; the variable "d" is set to 0.
; a   a2 
; b+c ab