Singular Manual: isFlat

| #### D.4.8.12 isFlat Procedure from library `homolog.lib` (see homolog_lib). Usage: isFlat(M); M module Return: 1 if M'=coker(M) is flat; 0 if this is not the case. Example:
    LIB "homolog.lib";
    ring A = 0,(x,y),dp;
    matrix M[3][3] = x-1,y,x,x,x+1,y,x2,xy+x+1,x2+y;
    print(M);
    ==> x-1,y,     x,
    ==> x,  x+1,   y,
    ==> x2, xy+x+1,x2+y
    isFlat(M);             // coker(M) is not flat over A=Q[x,y]
    ==> 0
    qring B = std(x2+x-y);   // the ring B=Q[x,y]/<x2+x-y>
    matrix M = fetch(A,M);
    isFlat(M);             // coker(M) is flat over B
    ==> 1
    setring A;
    qring C = std(x2+x+y);   // the ring C=Q[x,y]/<x2+x+y>
    matrix M = fetch(A,M);
    isFlat(M);             // coker(M) is not flat over C
    ==> 0

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