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D.15.18.11 twist

Procedure from library tateProdCplxNegGrad.lib (see tateProdCplxNegGrad_lib).

Usage:
twist(M,c); M module, c intvec

Purpose:
twists the module M by c

Assume:
M is a multigraded module

Return:
M with the new grading

Example:
 
LIB "tateProdCplxNegGrad.lib";
intvec c = 1,1;
def (S,E) = productOfProjectiveSpaces(c);
setring(S);
module M = freemodule(2);
intmat gradeM[2][2] = 0,1,0,1;
M = setModuleGrading(M,gradeM);
getModuleGrading(M);
==> 0,1,
==> 0,1 
intvec c = 2,2;
==> // ** redefining c (intvec c = 2,2;) ./examples/twist.sing:9
module Mtwist = twist(M,c);
getModuleGrading(Mtwist);
==> -2,-1,
==> -2,-1