Whoops, sorry for the bad code in my last message. I mean of course that the problem is that
ConT (mkName "[]") /= ListT Regards, Eric On Oct 7, 2012, at 12:08 , Eric M. Pashman <eric.pash...@gmail.com> wrote: > Nicolas, > > Intended usage seems to be something like > > AppT ListT $ ConT . mkName $ "Int" > > That works. So it seems that there is indeed no way to construct the > syntactically special list type from its (valid) name, but it can easily be > done as above. > > In my opinion, it should be possible to do what we've been trying -- ConT > (mkName "[]") `AppT` ConT "Char" -- or whatever. The problem seems simply to > be that > > ConT . mkName $ "[]" \= ListT > > I don't know the first thing about the GHC source, but I would imagine that's > easily fixable if the behavior we both expected is more broadly desired. > > Regards, > > Eric > > On Oct 7, 2012, at 11:24 , Nicolas Frisby <nicolas.fri...@gmail.com> wrote: > >> The issue you had with applications of the [] type seems to be more >> insidious than my last email made it out to be. This expression >> >> ( $(return $ ConE (mkName "[]")) :: >> $(return $ ConT (mkName "[]") `AppT` ConT ''Char) >> ) >> >> fails with "[] is applied to too many arguments". I'm thinking that >> the "[]" in the type is being resolved somehow to the the [] data >> constructor, not the [] type constructor. >> >> This seems specific to []; the following works for tuples, even though >> the data and type constructor also share a string name. >> >> $(return $ ConE (mkName "(,)") `AppE` LitE (CharL 'c') `AppE` LitE >> (CharL 'a')) :: >> $(return $ ConT (mkName "(,)") `AppT` ConT ''Char `AppT` ConT ''Char) >> >> I haven't yet narrowed down where the mkName'd string is >> (inappropriately?) resolved in the GHC source. >> >> Eric, special-casing for ArrowT probably avoids this problem for you. >> The only thing to glean from this email is that you ideally wouldn't >> need to worry about the special-casing for your current application — >> I think there's a TH bug at play, though I haven't found an open GHC >> ticket for it and it may very well still be a known issue. >> >> On Sun, Oct 7, 2012 at 10:15 AM, Eric M. Pashman <eric.pash...@gmail.com> >> wrote: >>> Nicolas, thanks for the welcome, and thanks for pointing out the additional >>> 'Type' constructors! >>> >>> I'd looked over the available constructors, but apparently not very well. >>> The 'ListT', 'TupleT', 'ArrowT', etc., constructors are precisely what I >>> need to make this work in a straightforward fashion. >>> >>> So I don't actually have a problem making the right 'Name' value, just a >>> problem reading the TH source. Well, that's that. ... >>> >>> Many thanks, >>> >>> Eric >> >> My pleasure. >> >> However, > _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users
