gap> arc:=[[2,4],[1,3],[2,4],[1,3]];;            
gap> f:=ArcPresentationToKnottedOneComplex(arc);
Map of regular CW-complexes

gap> comp:=RegularCWComplexComplement(f);
Testing contractibility...
151 out of 151 cells tested.
The input is compatible with this algorithm.
Regular CW-complex of dimension 3

