Excuse me for playing referee here, as I am looking at this discussion from a very abstract level, as I am a beginning functional-logic programmer. But my question (primarily for Fergus) is: "has Ashley shown in her example a means of automating a toUnits imperative in Haskell that must be done explicitly in Mercury?" If so, then we have the start of the Haskell-Mercury comparison document which shows an advantage of Haskell over Mercury.
I'm cross-posting this to the Libraries list...
At 2001-04-10 18:02, Fergus Henderson wrote:
Still, the need to insert explicit `toUnits' is annoying, and it would be nice to have a system where every number was already a dimensionless unit.
That's easy:
-- type Unit rep = Dimensioned Zero Zero Zero rep;
instance (Real a) => Real (Unit a) where { -- put instances here }; --
Of course you'll have to appropriately declare superclasses of Real, such as Num, Ord, Show, Eq etc.
-- Ashley Yakeley, Seattle WA
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