[Haskell-cafe] how to generate source code from TH Exp?
hi, i was wondering if it's possible to directly generate Haskell source code from a Template Haskell `Q Exp', i.e. use TH as a kind of preprocessor? i am asking because currently the iOS port of ghc doesn't support TH and i need to generate some instances for the persistent package [1,2]. i've been toying with fmap ppr . runQ $ q but the result needs to be edited by hand quite a bit. any ideas where to start? thanks, sk [1] http://hackage.haskell.org/package/persistent [2] http://hackage.haskell.org/package/persistent-template ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] how to generate source code from TH Exp?
Just pretty-print a Exp. It seems that show $ ppr exp will produce exactly what you need. The same goes for Dec (declarations), etc. 2011/5/12 Stefan Kersten s...@k-hornz.de: hi, i was wondering if it's possible to directly generate Haskell source code from a Template Haskell `Q Exp', i.e. use TH as a kind of preprocessor? i am asking because currently the iOS port of ghc doesn't support TH and i need to generate some instances for the persistent package [1,2]. i've been toying with fmap ppr . runQ $ q but the result needs to be edited by hand quite a bit. any ideas where to start? thanks, sk [1] http://hackage.haskell.org/package/persistent [2] http://hackage.haskell.org/package/persistent-template ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] how to generate source code from TH Exp?
On 5/12/11 4:03 PM, Serguey Zefirov wrote:
Just pretty-print a Exp.
It seems that show $ ppr exp will produce exactly what you need.
The same goes for Dec (declarations), etc.
ah ok, thanks!
fwiw, here's a way to extract a list of module names that need to be
imported, adapted from an example by Neil Mitchell using generics:
extractModules :: Data a = a - [String]
extractModules = sort . nub . everything (++) ([] `mkQ` f)
where f (NameQ x) = [modString x]
f (NameG _ _ x) = [modString x]
f _ = []
which can be used to output a source code module:
mkModule :: (Data a, Ppr a) = [String] - String - a - String
mkModule exts name e =
unlines ([ {-# LANGUAGE ++ intercalate , exts ++ #-}
, module ++ name ++ where ]
++ map (import qualified ++) (extractModules e))
++ show (ppr e)
good enough for now ;)
sk
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Re: [Haskell-cafe] how to generate source code from TH Exp?
On Thu, May 12, 2011 at 2:04 PM, Stefan Kersten s...@k-hornz.de wrote: extractModules = sort . nub . everything (++) ([] `mkQ` f) where f (NameQ x) = [modString x] f (NameG _ _ x) = [modString x] f _ = [] Minor nitpick: instead of doing 'sort . nub', please use 'import qualified Data.Set as S' and do 'S.toAscList . S.fromList'. This should be a lot faster. Cheers, =) -- Felipe. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] how to generate source code from TH Exp?
On Thursday 12 May 2011 19:14:09, Felipe Almeida Lessa wrote: On Thu, May 12, 2011 at 2:04 PM, Stefan Kersten s...@k-hornz.de wrote: extractModules = sort . nub . everything (++) ([] `mkQ` f) where f (NameQ x) = [modString x] f (NameG _ _ x) = [modString x] f _ = [] Minor nitpick: instead of doing 'sort . nub', please use 'import qualified Data.Set as S' and do 'S.toAscList . S.fromList'. This should be a lot faster. Or `map head . group . sort', which may be faster than building an intermediate Set (haven't benchmarked, may be faster, slower or mkae no difference). Cheers, =) ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
