IsLTrivial for finite finitely presented monoids

[james-d-mitchell]

Originally reported by: Nicolas M. Thiéry (Bitbucket: nthiery, GitHub: nthiery)

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Let's create the 0-Hecke monoid as a finitely presented monoid:

gap> LoadPackage("semigroups");
gap> M := FreeMonoid(2);
gap> m1 := M.1; m2 := M.2;
gap> H := M / [ [ m1^2, m1], [m2^2, m2], [m1*m2*m1, m2*m1*m2]];
gap> IsFinite(H);
true
gap> Size(H);
6
gap> JClasses(H);
[ {m1*m2*m1}, {m2*m1}, {m1}, {m1*m2}, {m2}, {<identity ...>} ]

This is all very nice!

Which makes the missing bit unexpected:

gap> IsLTrivial(H);
Error, no method found! For debugging hints type ?Recovery from NoMethodFound
Error, no 2nd choice method found for `IsLTrivial' on 1 arguments called from
<function "HANDLE_METHOD_NOT_FOUND">( <arguments> )
 called from read-eval loop at line 12 of *stdin*
you can 'quit;' to quit to outer loop, or
you can 'return;' to continue

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• Bitbucket: https://bitbucket.org/james-d-mitchell/semigroups/issue/146

[james-d-mitchell]

Original comment by Nicolas M. Thiéry (Bitbucket: nthiery, GitHub: nthiery):

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Thanks!

[james-d-mitchell]

Original comment by James Mitchell (Bitbucket: james-d-mitchell, GitHub: james-d-mitchell):

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This is fixed in the 3.0-dev branch and so this issue will be resolved when we release 3.0.

[james-d-mitchell]

This is resolved so I'm going to close the issue.