Your question is if I understand correctly, whether we can think of a type that has a law abiding Eq instance that gives equality as fine grained as extensional equality (meaning structural equality?) but for which no law abing instance of Ord can be given such that a <= b && a >= b ==> a == b This boils down to the question whether on each set with an equality relation defined on it a total ordering (consistent with the equality relation) can also be defined. One counterexample is the complex numbers. Does that answer your question? Cheers! On Jan 1, 2015 3:27 PM, "Tom Ellis" < tom-lists-haskell-cafe-2013@jaguarpaw.co.uk> wrote:
On Thu, Jan 01, 2015 at 03:22:55PM +0100, Atze van der Ploeg wrote:
i want it to be at least as fine grained as extensional equivalence
Then see Oleg's comment or am i missing something here?
Perhaps you could explain Oleg's comment. I don't understand it. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe