[Haskell-cafe] An issue with EDSLs in the ``finally tagless''
peteg42 at gmail.com
Thu Sep 24 01:10:03 EDT 2009
On 24/09/2009, at 2:45 PM, Brad Larsen wrote:
> On Thu, Sep 24, 2009 at 12:22 AM, Peter Gammie <peteg42 at gmail.com>
>> Ambiguity is IMHO best handled with a judicious application of type
>> 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
> 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!
More information about the Haskell-Cafe