[Haskell-cafe] Re: Justification for Ord inheriting from Eq?

[ihope]

On 4/7/06, Jared Updike <jupdike at gmail.com> wrote:
> > given an Ord instance (for a type T) a corresponding Eq instance can be
> > given by:
> >
> > instance Eq T where
> >     a == b = compare a b == EQ
>
> where did this second -----^ == come from? (I guess if if Ordering
> derives Eq :-) I think you meant
>
> > instance (Ord T) => Eq T where
> >     a == b = case compare a b of
> >                     EQ -> True
> >                     _ -> False

Both work the same. Here's an intermediate form:

a == b =
  if compare a b == EQ
  then True
  else False