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D.6.3.3 corank

Procedure from library classify.lib (see classify_lib).

Usage:
corank(f); f=poly

Return:
the corank of the Hessian matrix of f, of type int

Remark:
corank(f) is the number of variables occuring in the residual singularity after applying 'morsesplit' to f

Example:
 
LIB "classify.lib";
ring r=0,(x,y,z),ds;
poly f=(x2+3y-2z)^2+xyz-(x-y3+x2*z3)^3;
corank(f);
==> 2