D.4.3.16 kontrahom

Procedure from library homolog.lib (see homolog_lib).

Usage:

kontrahom(A,k); A=matrix, k=integer

Return:

matrix Hom(A,R^k), i.e. let A be a matrix defining a map F1–>F2 of free R-modules, then the matrix of Hom(F2,R^k)–>Hom(F1,R^k) is computed (R=basering).

Example:

LIB "homolog.lib";
ring r;
matrix n[2][3]=x,y,5,z,77,33;
print(kontrahom(n,3));
→ x,z, 0,0, 0,0, 
→ y,77,0,0, 0,0, 
→ 5,33,0,0, 0,0, 
→ 0,0, x,z, 0,0, 
→ 0,0, y,77,0,0, 
→ 0,0, 5,33,0,0, 
→ 0,0, 0,0, x,z, 
→ 0,0, 0,0, y,77,
→ 0,0, 0,0, 5,33