Subsemigroups of quotient semigroups

[artemiskonst]

Factorization() and IsomorphismFpSemigroup() do not work with subsemigroups of quotient semigroups. SubsemigroupNC does not work either. Below, T = Q = H and the commands work with T but not Q or H.

gap> S := Semigroup([ Transformation( [ 2, 1, 5, 1, 5 ] ), Transformation( [ 1, 1, 1, 5, 3 ] ), Transformation( [ 2, 5, 3, 5, 3 ] ) ]);;
gap> congs := CongruencesOfSemigroup(S);;
gap> cong := congs[3];;
gap> T := S / cong;;
gap> gens := GeneratorsOfSemigroup(S);;
gap> images := List(gens, gen -> EquivalenceClassOfElement(cong, gen));;  
gap> Q := Subsemigroup(T, images);
<semigroup with 3 generators>
gap> Q = T;
true
gap> Factorization(T, images[2]);
[ 2 ]
gap> Factorization(Q, images[2]);
Error, no method found! For debugging hints type ?Recovery from NoMethodFound
Error, no 1st choice method found for `Factorization' on 2 arguments at /Users/artemiskonst/gap/lib/methsel2.g:249 called from
<function "HANDLE_METHOD_NOT_FOUND">( <arguments> )
 called from read-eval loop at *stdin*:35
type 'quit;' to quit to outer loop
brk> quit;

gap> H := SubsemigroupNC(T, images);
<semigroup with 3 generators>
gap> T = H;
true
gap> Factorization(H, images[2]);
Error, no method found! For debugging hints type ?Recovery from NoMethodFound
Error, no 1st choice method found for `Factorization' on 2 arguments at /Users/artemiskonst/gap/lib/methsel2.g:249 called from
<function "HANDLE_METHOD_NOT_FOUND">( <arguments> )
 called from read-eval loop at *stdin*:38
type 'quit;' to quit to outer loop
brk> quit;

gap> map := IsomorphismFpSemigroup(T);
MappingByFunction( <quotient of <semigroup congruence over <transformation semigroup of size 59, degree 5 with 3 generators> with 1 generating pairs>>, <fp semigroup on the generators 
[ s1, s2, s3 ]>, function( x ) ... end, function( x ) ... end )
gap> map := IsomorphismFpSemigroup(Q);                
Error, no method found! For debugging hints type ?Recovery from NoMethodFound
Error, no 2nd choice method found for `IsomorphismFpSemigroup' on 1 arguments at /Users/artemiskonst/gap/lib/methsel2.g:249 called from
<function "HANDLE_METHOD_NOT_FOUND">( <arguments> )
 called from read-eval loop at *stdin*:33
type 'quit;' to quit to outer loop
brk> quit;
gap> IsomorphismFpSemigroup(H);  
Error, no method found! For debugging hints type ?Recovery from NoMethodFound
Error, no 2nd choice method found for `IsomorphismFpSemigroup' on 1 arguments at /Users/artemiskonst/gap/lib/methsel2.g:249 called from
<function "HANDLE_METHOD_NOT_FOUND">( <arguments> )
 called from read-eval loop at *stdin*:38
type 'quit;' to quit to outer loop
brk> quit;

[james-d-mitchell]

Resolved in v4.0.3