| #### D.4.11.17 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

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