Dear GAP forum,
I'm sure I'm missing something, but I can't understand the difference
a) IsBinaryRelation( R ); ^^^ b) IsSymmetricBinaryRelation( rel ). ^^^^^
For example, if I write:
gap> A := Domain([1,2,3,4]);;
gap> elems := [Tuple([1,1]),Tuple([2,2]),Tuple([3,3]),Tuple([4,4]),
gap> R := GeneralMappingByElements(A, A, elems);
<general mapping: <object> -> <object> >
Error no method found for operation IsSymmetricBinaryRelation with 1
How many arguments does "rel" mean? (Other argument sets, such as "A, A,
elems", "R, elems", "elems", etc. don't work either.)
If I write:
gap> R := EquivalenceRelationByPartition(A, [[1,3],[2,4]]);
<equivalence relation on <object> >
gap> IsSymmetricBinaryRelation(R); # one argument!
it works. But if I assign an equivalence relation to R, I already know
that it is a symmetric, reflexive and transitive relation!
Please, could anybody tell me what I'm missing?