Brad,
On 24/09/2009, at 2:45 PM, Brad Larsen wrote:
On Thu, Sep 24, 2009 at 12:22 AM, Peter Gammie <pete...@gmail.com>
wrote:
[...]
Ambiguity is IMHO best handled with a judicious application of type
(or
data) families, but you can get surprisingly far by simply
requiring that
every class member mention all type variables in the class head.
YMMV of
course.
Can you say more about the use of type/data families?
Multi-parameter type classes generally lead to ambiguity - see the
classic paper(s) by Simon PJ et al for some good examples.
In the context of Arrows, I used type/data families to make the
representation type (e.g. Integer) a function of the arrow (e.g. a
direct semantics), which makes life a bit easier for using this stuff
but is not completely faithful to what I wanted. (Imagine you want to
mix Integer and Double in the same expression.)
Hope this helps!
cheers
peter
--
http://peteg.org/
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