Tom Pledger <[EMAIL PROTECTED]> writes
> May we please have a partial order class in Haskell at some stage? It
> can be done outside the prelude (see below), but would be nicer inside
> (see below, removing all the tildes and primes).
>
> Something similar could be done with abstract algebra above the Num
> and Fractional classes: Group defining (+), negate, (-), and zero;
> Ring defining (*); and Field defining (/), recip, and one. I'm not so
> fussed about these, though.
>
> data PartialOrdering = PLT | PEQ | PGT | PUnrelated
> deriving (Eq, Ord, Ix, Enum, Read, Show, Bounded)
Year and half ago all these things, and many others, were suggested
in
http://www.botik.ru/pub/local/Mechveliani/basAlgPropos/
There the partial ordering was compare_m :: a -> a -> Maybe Ordering
------------------
Sergey Mechveliani
[EMAIL PROTECTED]
