Hi Bas,<br><br><div class="gmail_quote">On Wed, Dec 21, 2011 at 23:02, Bas van Dijk <span dir="ltr"><<a href="mailto:v.dijk.bas@gmail.com">v.dijk.bas@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div class="im">On 21 December 2011 19:29, Ian Lynagh <<a href="mailto:igloo@earth.li">igloo@earth.li</a>> wrote:<br>
</div><div class="im">> * There is a new feature constraint kinds (-XConstraintKinds):<br>
> <a href="http://www.haskell.org/ghc/dist/stable/docs/html/users_guide/constraint-kind.html" target="_blank">http://www.haskell.org/ghc/dist/stable/docs/html/users_guide/constraint-kind.html</a><br>
<br>
</div>I'm trying to run the ConstraintKinds example from the documentation:<br>
<br>
{-# LANGUAGE ConstraintKinds, TypeFamilies #-}<br>
type family Typ a b :: Constraint<br>
type instance Typ Int b = Show b<br>
type instance Typ Bool b = Num b<br>
<br>
But GHC complains:<br>
Not in scope: type constructor or class `Constraint'<br>
<br>
Do I have to import some GHC module for this?<br></blockquote><div><br>Yes: GHC.Prim.<br><br>(Which reminds me, Simon, we had agreed to re-export Constraint from GHC.Exts, but it wasn't clear to me how to do this, since Constraint is a kind, not a type, so it can't just go on the export list of the module...)<br>
<br><br>Cheers,<br>Pedro<br> </div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
Cheers,<br>
<br>
Bas<br>
<div class="HOEnZb"><div class="h5"><br>
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