EquivalenceClasses of trivial congruence returns empty list

Issue #94 resolved
Michael Torpey
created an issue

(Library)

The EquivalenceClasses function returns the empty list for a trivial semigroup congruence by generating pairs.

gap> S:=FullTransformationSemigroup(6);;
gap> R:=PrincipalFactor(Random(DClasses(S)));;
gap> cong := SemigroupCongruenceByGeneratingPairs(R, [ ]);;
gap> EquivalenceClasses(cong);
[  ]

Comments (8)

  1. James Mitchell repo owner

    Same as in Issue #95:

    gap> S:=FullTransformationSemigroup(6);;
    gap> R:=PrincipalFactor(Random(DClasses(S)));;
    gap> cong := SemigroupCongruenceByGeneratingPairs(R, [ ]);;
    gap> EquivalenceClasses(cong);
    Error, List Element: <list>[1] must have an assigned value in
      ht := HTCreate( pairs[1], rec(
          forflatplainlists := true,
          treehashsize := s!.opts.hashlen.L ) ); called from 
    SEMIGROUPS_SetupCongData( cong ); called from
    AsLookupTable( cong ) called from
    <function "unknown">( <arguments> )
     called from read-eval loop at line 21 of *stdin*
    you can 'return;' after assigning a value
    brk> 
    
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