truncate standard basis result matrix [variable list]

Create the matrix whose columns generate the submodule of M, of all elements of M of degree at least d, where M is the module presented by the given standard basis, and d is an integer for which the user is prompted.

The result matrix consists of a k-basis of M in degree d, and the set of column unit vectors corresponding to those rows of degree at least d. Each column of the result matrix is a monomial in the variables specified in the variable list.

For example, if the variables are ``abcd'', and the variables are all in one block,

%  type m
; a a2 b4 
; b c2 c4 

%  std m m
; 12.3.4.5.6.7.8.
; computation complete after degree 8

%  putstd m ms

%  type ms
; b4 a 0         0      0     0         
; c4 b b4c2-a2c4 b5-ac4 ab-c2 a3c4-b3c4 

%  truncate ms m1
! lowest degree (default=0)  ?  1
; warning: no standard basis. Using initial terms of matrix

%  type m1
; b c d 0 0 0 0 
; 0 0 0 a b c d