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D.2.6.4 freerank
Procedure from library poly.lib (see poly_lib).
- Usage:
- freerank(M[,any]); M=poly/ideal/vector/module/matrix
- Compute:
- rank of module presented by M in case it is free.
By definition this is vdim(coker(M)/m*coker(M)) if coker(M)
is free, where m is the maximal ideal of the variables of the
basering and M is considered to be a matrix.
(the 0-module is free of rank 0)
- Return:
- rank of coker(M) if coker(M) is free and -1 else;
in case of a second argument return a list:
L[1] = rank of coker(M) or -1
L[2] = minbase(M)
- Note:
- freerank(syz(M)); computes the rank of M if M is free (and -1 else)
Example:
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