[GAP Forum] Semigroup homomorphism
Jose Joao Morais
jjoao at netcabo.pt
Thu Jan 22 18:33:59 GMT 2004
Dear GAP Forum,
I am trying to define a semigroup homomorphism, so I looked at the code
for GroupGeneralMappingByImages in ghom.gi and tried to do something
similar for semigroups. This is what I did (poi5 is a semigroup of
transformations)
gap> G:=poi5;
<monoid with 5 generators>
gap> H:=G;
<monoid with 5 generators>
gap> filter:=HasSource and HasRange and HasMappingGeneratorsImages;
<Operation "<<and-filter>>">
gap> gens:=GeneratorsOfSemigroup(G);;
gap> imgs:=GeneratorsOfSemigroup(H);;
gap> mapi:=[Immutable(gens),Immutable(imgs)];;
gap> hom:=rec();
rec( )
gap> ObjectifyWithAttributes( hom,
> NewType( GeneralMappingsFamily
> ( ElementsFamily( FamilyObj( G ) ),
> ElementsFamily( FamilyObj( H ) ) ), filter ),
> Source,G,
> Range,H,
> MappingGeneratorsImages,mapi);
gap> SetIsMapping( hom, true );
gap> IsMapping(hom);
true
gap> Source(hom);
Error, no method found! For debugging hints type ?Recovery from
NoMethodFound
Error, no 1st choice method found for `Source' on 1 arguments called
from
<function>( <arguments> ) called from read-eval-loop
Entering break read-eval-print loop ...
you can 'quit;' to quit to outer loop, or
you can 'return;' to continue
I could not find the code for Source, so I would like to ask if
someone could tell me why this error happened or how can make this work.
Thank you
Jose Morais
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