D.15.22.4 fPiece

Usage:

fPiece(I,a,b); I = ideal, a = poly, b = poly.

Assume:

I is the ideal generated by the monomials w.r.t. faces, a-b is the degree of the graded piece.

Return:

graded piece (of degree a-b) of first order deformation on ideal I.

Theory:

The procedure will compute the graded pieces of the first order deformaiton which has degree a-b.

LIB "stanleyreisner.lib";
ring R=0,(x(1..4)),lp;
ideal i=x(1),x(2),x(3),x(4),x(1)*x(4),x(2)*x(4),x(1)*x(3),x(2)*x(3);
FirstOrderDeformation phi=fPiece(i,x(4)^2,x(1)*x(2));
phi;
==> x(1),x(2),x(3),x(4),x(1)*x(4),x(2)*x(4),x(1)*x(3),x(2)*x(3)  ->  1
==> phi.source  ->  phi.over / phi.source
==>