[Haskell-cafe] ghc api printing of types

Phyx lonetiger at gmail.com
Sun Jul 4 12:44:24 EDT 2010


Thanks for the reply, I've taken a look at the implementation of
pprTypeForUser and it should do what I want but doesn't :(
My function is

printType :: PrintUnqualified -> Type.Type -> String
printType qual = showSDocForUser qual . pprTypeForUser False

but I still don't get the predicates printer out

"(t_amCk, [a]) -> (t_amCk, [a]) -> (t_amCk, [a])" is what I get instead of
"Num t => (t, [a]) -> (t, [a]) -> (t, [a])"


Guess I'll go take a look at hint to see if it does anything else


-----Original Message-----
From: Daniel Gorín [mailto:dgorin at dc.uba.ar] 
Sent: Sunday, July 04, 2010 15:49
To: Phyx
Cc: haskell-cafe at haskell.org
Subject: Re: [Haskell-cafe] ghc api printing of types

I believe the way is done in hint is something like this (untested):

showType t =
   do -- Unqualify necessary types
      -- (i.e., do not expose internals)
       unqual <- GHC.getPrintUnqual
      return $ GHC.showSDocForUser unqual (GHC.pprTypeForUser False   
t) -- False means 'drop explicit foralls'

Hope that helps


On Jul 4, 2010, at 8:36 AM, Phyx wrote:

> I was wondering how given a Type I can get a pretty printed type out 
> of it.
> I’m currently using showSDocUnqual . pprType . snd . tidyOpenType 
> emptyTidyEnv But this has the problem that predicates don’t get 
> printed, anyone know how GHCi does this?
> Thanks,
> Phyx
> _______________________________________________
> Haskell-Cafe mailing list
> Haskell-Cafe at haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe

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