73.78 XModDerivationByImages

XModDerivationByImages( X, im )

This function takes a list of images in S = X.source for the generators of R = X.range and constructs a map chi : R to S which is then tested to see whether the axioms of a derivation are satisfied.

    gap> XSC;
    Crossed module [c3->s3]
    gap> imchi := [ (1,2,3)(4,6,5), (1,2,3)(4,6,5) ];;
    gap> chi := XModDerivationByImages( XSC, imchi );
    XModDerivationByImages( s3, c3, [ (4,5,6), (2,3)(5,6) ], 
       [ (1,2,3)(4,6,5), (1,2,3)(4,6,5) ] )  

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