ConjugationXMod( R [,S] )
This construction returns the crossed module whose source S is a normal subgroup of the range R, the boundary is the inclusion map, the group of automorphisms is the inner automorphism group of S, and the action maps an element of r in R to conjugation of S by r. The default value for S is R.
gap> s4 := Group( (1,2,3,4), (1,2) );; gap> a4 := Subgroup( s4, [ (1,2,3), (2,3,4) ] );; gap> k4 := Subgroup( a4, [ (1,2)(3,4), (1,3)(2,4) ] );; gap> s4.name := "s4";; a4.name := "a4";; k4.name := "k4";; gap> CX := ConjugationXMod( a4, k4 ); Crossed module [k4->a4]
GAP 3.4.4