Thanks Richard ! I followed your advice and posted a new comment to the ticket
Yorick 2014/1/6 Richard Eisenberg <[email protected]> > Hello Yorick, > > Thanks for taking this one on! > > First off, this kind of question/post is appropriate for putting right > into the ticket itself. Posting a comment to the ticket makes it more > likely that you'll get a response and saves your thoughts for posterity. > > Now, on to your question: > > That seems somewhat reasonable, but I think your work could go a little > further. It looks like you've introduced TupleP as a new constructor for > Pred. This, I believe, would work. But, I think it would be better to have > a way of using *any* type as a predicate in TH, as allowed by > ConstraintKinds. Perhaps one way to achieve this is to make Pred a synonym > of Type, or there could be a TypeP constructor for Pred. > > In any case, I would recommend writing a wiki page up with a proposed new > TH syntax for predicates and then posting a link to the proposal on the > #7021 ticket. Then, it will be easier to debate the merits of any > particular approach. > > Once again, thanks! > Richard > > On Jan 3, 2014, at 6:13 PM, Yorick Laupa wrote: > > Hi, > > I try to make my way through #7021 [1]. Unfortunately, there is nothing in > the ticket about what should be expected from the code given as example. > > I came with an implementation and I would like feedback from you guys. So, > considering this snippet: > > -- > > {-# LANGUAGE ConstraintKinds #-} > > type IOable a = (Show a, Read a) > > foo :: IOable a => a > foo = undefined > > -- > > This is what I got now when pretty-printing TH.Info after reify "foo" > call: > > VarI Tuple.foo (ForallT [PlainTV a_1627398594] [TupleP 2 [AppT (ConT > GHC.Show.Show) (VarT a_1627398594),AppT (ConT GHC.Read.Read) (VarT > a_1627398594)]] (VarT a_1627398594)) Nothing (Fixity 9 InfixL) > > Does that sound right to you ? > > Thanks for your time > > -- Yorick > > [1] https://ghc.haskell.org/trac/ghc/ticket/7021 > _______________________________________________ > ghc-devs mailing list > [email protected] > http://www.haskell.org/mailman/listinfo/ghc-devs > > >
_______________________________________________ ghc-devs mailing list [email protected] http://www.haskell.org/mailman/listinfo/ghc-devs
