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7.3.9 intersect (plural)
Syntax:
intersect (expression_list of ideal_expression )
intersect (expression_list of module_expression )
Type:
- ideal, resp. module
Purpose:
- computes the intersection of ideals, resp. modules.
Example:
| | ring r=0,(x,y),dp;
def R=nc_algebra(-1,0); //anti-commutative algebra
setring R;
module M=[x,x],[y,0];
module N=[0,y^2],[y,x];
option(redSB);
module Res;
Res=intersect(M,N);
print(Res);
==> y2, 0,
==> -xy,xy2
kill r,R;
//--------------------------------
LIB "ncalg.lib";
ring r=0,(x,d),dp;
def RR=Weyl(); // make r into Weyl algebra
setring RR;
ideal I = x+d^2;
ideal J = d-1;
ideal H = intersect(I,J);
H;
==> H[1]=d4+xd2-2d3-2xd+d2+x+2d-2
==> H[2]=xd3+x2d-xd2+d3-x2+xd-2d2-x+1
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