[mercury-users] typeclass constraint on type definition... wrong

[David Glen JEFFERY]

On 28-May-1999, Fergus Henderson <fjh at cs.mu.OZ.AU> wrote:
> 
> Our original design for type classes in Mercury was deliberately
> conservative.  This particular feature of Haskell had been
> debated quite a bit in the Haskell community, and there had
> been suggestions by some of the prominent Haskell researchers
> that this feature ought to be dropped in Haskell 98.
> Given our aim of starting off with a fairly conservative design,
> I think leaving out type class constraints on data type definitions
> was the right decision at the time.
> 
> However, I think Richard is right and the Haskell people who suggested
> dropping the feature in Haskell 98 were wrong.  Therefore I think it
> would be a good idea to support type class constraints on data type
> declarations in a future version of Mercury.

Agreed on both points. I'll put it on my todo list.


dgj
-- 
David Jeffery (dgj at cs.mu.oz.au) |  Marge: Homer, is this how you pictured
PhD student,                    |         married life?
Dept. of Comp. Sci. & Soft. Eng.|  Homer: Yup, pretty much... except we
The University of Melbourne     |         drove around in a van solving
Australia                       |         mysteries.
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