準クォートとTemplate Haskell

TemplateHaskellとか準クォートに興味があったので触ってみました。
型プログラミングの手助けになるモジュールを作ってみたいな、と思いつつ今回はとりあえず型の表示をさせてみることにします。

TypeChecker.hs

{-# LANGUAGE TemplateHaskell, QuasiQuotes #-}
module TypeChecker where

import Language.Haskell.TH
import Language.Haskell.TH.Quote

import Text.Regex.Posix
import qualified Data.Text as Text

type FunctionList = [Name]

parseFunc :: String -> Maybe FunctionList
parseFunc s = do
  mList <- mayToList s
  return $ map mkName mList

mayToList :: String -> Maybe [String]
mayToList s =
  case s =~ "^\\[(.*)\\]$" :: Bool of
    True -> Just $ (map (Text.unpack . Text.strip) s'')
    False -> Nothing

  where
    s'' :: [Text.Text]
    s'' = Text.splitOn (Text.pack ",") (Text.tail $ Text.init s')

    s' :: Text.Text
    s' = Text.pack s

fList :: QuasiQuoter
fList = QuasiQuoter { quoteExp = parseExp,
                      quotePat = undefined,
                      quoteType = undefined,
                      quoteDec = undefined }

parseExp :: String -> ExpQ
parseExp s =
  case parseFunc s of
    Just fs -> do
      info <- mapM reify fs
      runIO $ putStrLn $ pprint info
      return $ AppE (VarE 'return) (ConE '())
    Nothing -> undefined

ghciで起動させるなら -XTemplateHaskell -XQuasiQuotes のオプションと import Language.Haskell.TH が必要です。
[fList|[a,b,c,d]|]などとすれば、定義済みの函数a,b,c,dの型を表示してくれます。

---

実行例

~$ ghci -XTemplateHaskell -XQuasiQuotes
GHCi, version 7.4.1: http://www.haskell.org/ghc/  :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Prelude> import Language.Haskell.TH
Prelude Language.Haskell.TH> :l TypeChecker.hs 
[1 of 1] Compiling TypeChecker      ( TypeChecker.hs, interpreted )
Ok, modules loaded: TypeChecker.
*TypeChecker Language.Haskell.TH> [fList|[print, curry, $, mapM]|]
Loading package array-0.4.0.0 ... linking ... done.
Loading package deepseq-1.3.0.0 ... linking ... done.
Loading package bytestring-0.9.2.1 ... linking ... done.
Loading package containers-0.4.2.1 ... linking ... done.
Loading package transformers-0.2.2.0 ... linking ... done.
Loading package mtl-2.0.1.0 ... linking ... done.
Loading package regex-base-0.93.2 ... linking ... done.
Loading package pretty-1.1.1.0 ... linking ... done.
Loading package regex-posix-0.95.1 ... linking ... done.
Loading package text-0.11.1.13 ... linking ... done.
Loading package template-haskell ... linking ... done.
System.IO.print :: forall a_0 . GHC.Show.Show a_0 =>
                                a_0 -> GHC.Types.IO ()
Data.Tuple.curry :: forall a_1 b_2 c_3 . ((a_1, b_2) -> c_3) ->
                                         a_1 -> b_2 -> c_3
GHC.Base.$ :: forall a_4 b_5 . (a_4 -> b_5) -> a_4 -> b_5
infixr 0 GHC.Base.$
Control.Monad.mapM :: forall (m_6 :: * -> *) a_7 b_8 . GHC.Base.Monad m_6 =>
                                                       (a_7 -> m_6 b_8) -> [a_7] -> m_6 ([b_8])