On 1/9/12 7:54 AM, Luminous Fennell wrote:
On Mon, Jan 09 2012 at 10:37 +0100, Steve Horne wrote:
On 08/01/2012 21:13, Brandon Allbery wrote:
(Also, de facto I think it's already more or less been decided in
favor of type families, just because functional dependencies are (a)
a bit alien [being a glob of Prolog-style logic language imported
into the middle of System Fc] and (b) [as I understand it] difficult
to verify that the code in the compiler is handling all the
potential corner cases right [mainly because of (a)].
Isn't Haskell doing some prolog-ish things anyway?
I thought the compiler must be doing unification to resolve type
inference within expressions.
Even quite basic type reconstruction (e.g. for ML) needs unification, see e.g.
Pierce
TaPL chapter 22. The algorithm is rather easy to understand and implement.
Though it can be somewhat involved to optimize, since the naive
implementation is really quite inefficient. If you don't want to worry
about the details, there's always:
http://hackage.haskell.org/package/unification-fd
--
Live well,
~wren
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