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D.15.18.1 isAface

Procedure from library gitfan.lib (see gitfan_lib).

Usage:
isAface(a,gam0); a: ideal, gam0:intvec

Purpose:
Checks whether gam0 is an a-face w.r.t. the ideal a.

Return:
int

Example:
 
LIB "gitfan.lib";
ring R = 0,(T(1..4)),dp;
ideal I = T(1)*T(2)-T(4);
intvec w = 1,4;
intvec v = 1,2,4;
isAface(I,w); // should be 0
==> (T(1),T(4))
==> [1]:
==>    0
==> [2]:
==>    [1]:
==>       T(1)
==>    [2]:
==>       T(4)
==> [3]:
==>    [1]:
==>       [1]:
==>          wp
==>       [2]:
==>          1,1
==>    [2]:
==>       [1]:
==>          C
==>       [2]:
==>          0
==> [4]:
==>    _[1]=0
==> 0
isAface(I,v); // should be 1
==> (T(1),T(2),T(4))
==> [1]:
==>    0
==> [2]:
==>    [1]:
==>       T(1)
==>    [2]:
==>       T(2)
==>    [3]:
==>       T(4)
==> [3]:
==>    [1]:
==>       [1]:
==>          wp
==>       [2]:
==>          1,1,1
==>    [2]:
==>       [1]:
==>          C
==>       [2]:
==>          0
==> [4]:
==>    _[1]=0
==> 1