On 04/01/2012 16:47, Steve Horne wrote: > > (a == a) > reflexivity : (a == b) => (b == a) > transitivity : (a == b) && (b == c) => (a == c) > Oops - that's... reflexivity : (a == a) symmetry : (a == b) => (b == a) transitivity : (a == b) && (b == c) => (a == c) An equivalence relation is a relation that meets all these conditions.