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>

On Thursday 12 May 2011 19:14:09, Felipe Almeida Lessa wrote:

On Thu, May 12, 2011 at 2:04 PM, Stefan Kersten 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, =)

On Sunday 15 May 2011 15:32:03, Herbert Valerio Riedel wrote:

On Thu, 2011-05-12 at 19:31 +0200, Daniel Fischer wrote:

...

...

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).

if the input list has _many_ duplicates, wouldn't using 'map head . group . sort' require more memory than going the 'toAscList . fromList' way?

Good point. Yes, it would (consider `replicate maxBound 1'). So `map head . group . sort' might be faster for lists with few duplicates, but it has worse worst-case complexity, so it's safer to use `toAscList . fromList'. Even in the where it's slower, it probably wouldn't make too much of a difference.