[Haskell-cafe] ordNub

Tom Ellis tom-lists-haskell-cafe-2013 at jaguarpaw.co.uk
Thu Jan 1 15:01:55 UTC 2015

On Thu, Jan 01, 2015 at 03:52:26PM +0100, Atze van der Ploeg wrote:
> If we do not require that (a <= b) && (a >= b) ==> a == b (where <= is
> from the total ordering and == is from the equality relation) then it is
> trivial, take the total ordering forall x y.  x <= y that i mentioned
> earlier.
> So the compatiblity with equality (you say field structure) is not besides
> the point, in fact antisymmetry means that the ordering corresponds to the
> equality relation.
> Clear now or did I misunderstand?

Here is my proposed equality and ordering on the complex numbers:

    data Complex = Complex (Double, Double) deriving (Eq, Ord)

Does this violate any of my requested conditions?

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