Add IsOrthoGroup property

Author: tomcontileslie

gap/attributes/properties.gd

@@ -102,3 +102,6 @@ DeclareProperty("IsSurjectiveSemigroup", IsSemigroup);
 InstallTrueMethod(IsSurjectiveSemigroup, IsRegularSemigroup);
 InstallTrueMethod(IsSurjectiveSemigroup, IsMonoidAsSemigroup);
 InstallTrueMethod(IsSurjectiveSemigroup, IsIdempotentGenerated);
+
+DeclareProperty("IsOrthogroup", IsSemigroup);
+DeclareSynonym("IsOrthoGroup", IsOrthogroup);

gap/attributes/properties.gi

@@ -1784,3 +1784,9 @@ x -> UnderlyingSemigroupOfSemigroupWithAdjoinedZero(x) <> fail);
 InstallMethod(IsSurjectiveSemigroup, "for a semigroup",
 [IsSemigroup],
 S -> IsEmpty(IndecomposableElements(S)));
+
+InstallMethod(IsOrthogroup, "for a semigroup",
+[IsSemigroup],
+function(S)
+  return IsCompletelyRegularSemigroup(S) and IsOrthodoxSemigroup(S);
+end);