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D.4.11.13 isLocallyFree
Procedure from library homolog.lib (see homolog_lib).
- Usage:
- isLocallyFree(M,r); M module, r int
- Return:
- 1 if M'=coker(M) is locally free of constant rank r;
0 if this is not the case.
Example:
| | LIB "homolog.lib";
ring R=0,(x,y,z),dp;
matrix M[2][3]; // the presentation matrix
M=x-1,y-1,z,y-1,x-2,x;
ideal I=fitting(M,0); // 0-th Fitting ideal of coker(M)
qring Q=I;
matrix M=fetch(R,M);
isLocallyFree(M,1); // as R/I-module, coker(M) is locally free of rk 1
==> 1
isLocallyFree(M,0);
==> 0
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