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Fix issue 1177 #1188

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Merged
james-d-mitchell merged 1 commit into from
May 19, 2026
Merged

Fix issue 1177 #1188

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5 changes: 3 additions & 2 deletions gap/semigroups/semigraph.gi
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Original file line number Diff line number Diff line change
Expand Up @@ -188,16 +188,17 @@ function(x, n)
end);

InstallMethod(\<, "for elements of a graph inverse semigroup",
IsIdenticalObj,
[IsGraphInverseSemigroupElement, IsGraphInverseSemigroupElement],
{x, y} -> x![1] < y![1]);

InstallMethod(\=, "for elements of a graph inverse semigroup",
IsIdenticalObj,
[IsGraphInverseSemigroupElement, IsGraphInverseSemigroupElement],
{x, y} -> x![1] = y![1]);

# here

InstallMethod(\*, "for elements of a graph inverse semigroup",
IsIdenticalObj,
[IsGraphInverseSemigroupElement, IsGraphInverseSemigroupElement],
function(x, y)
local type, graph, range, source, xobj, yobj, i, j;
Expand Down
20 changes: 20 additions & 0 deletions tst/standard/semigroups/semigraph.tst
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@
##

#@local D, DigraphNrVertices, DigraphRange, DigraphSource, S, gr, s, x, y
#@local G, H
gap> START_TEST("Semigroups package: standard/semigroups/semigraph.tst");
gap> LoadPackage("semigroups", false);;

Expand Down Expand Up @@ -128,6 +129,25 @@ gap> S := GraphInverseSemigroup(D);
gap> VerticesOfGraphInverseSemigroup(S);
[ v_1, v_2, v_3, v_4, v_5, v_6, v_7, v_8, v_9, v_10, v_11, v_12 ]

# Issue 1177 - check FamilyObj for graph inverse semigroup element binary ops
gap> D := Digraph([[4, 5], [1, 3, 4, 5], [1, 4, 5], [], [4]]);
<immutable digraph with 5 vertices, 10 edges>
gap> G := GraphInverseSemigroup(D);
<finite graph inverse semigroup with 5 vertices, 10 edges>
gap> H := GraphInverseSemigroup(D);
<finite graph inverse semigroup with 5 vertices, 10 edges>
gap> G = H;
false
gap> G.1 in H;
false
gap> G.1 < H.1;
Error, no method found! For debugging hints type ?Recovery from NoMethodFound
Error, no 1st choice method found for `<' on 2 arguments
gap> G.1 < G.1;
false
gap> G.1 = H.1;
false

#
gap> SEMIGROUPS.StopTest();
gap> STOP_TEST("Semigroups package: standard/semigroups/semigraph.tst");
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