[英]Is there a way how to enumerate all functions in a module using Template Haskell?
不幸的是,模板Haskell目前沒有這樣的功能。 所有解決方案都涉及解析模塊的源代碼。 但是,TH的location
和loc_filename
函數可以很容易地使用調用splice定位模塊。
這是從我的一個項目的源代碼中提取的解決方案:
{-# LANGUAGE LambdaCase, TupleSections #-}
import Language.Haskell.TH
import qualified Data.Attoparsec.Text as AP
import qualified Data.Text.IO as Text
import qualified Data.Text as Text
import qualified Data.Char as Char
import Data.Maybe
import Data.List
import Control.Applicative
import Data.Traversable
import Prelude hiding (mapM)
reifyLocalFunctions :: Q [(Name, Type)]
reifyLocalFunctions =
listTopLevelFunctionLikeNames >>=
mapM (\name -> reifyFunction name >>= mapM (return . (name, ))) >>=
return . catMaybes
where
listTopLevelFunctionLikeNames = do
loc <- location
text <- runIO $ Text.readFile $ loc_filename loc
return $ map (mkName . Text.unpack) $ nub $ parse text
where
parse text =
either (error . ("Local function name parsing failure: " ++)) id $
AP.parseOnly parser text
where
parser =
AP.sepBy (optional topLevelFunctionP <* AP.skipWhile (not . AP.isEndOfLine))
AP.endOfLine >>=
return . catMaybes
where
topLevelFunctionP = do
head <- AP.satisfy Char.isLower
tail <- many (AP.satisfy (\c -> Char.isAlphaNum c || c `elem` ['_', '\'']))
return $ Text.pack $ head : tail
reifyFunction :: Name -> Q (Maybe Type)
reifyFunction name = do
tryToReify name >>= \case
Just (VarI _ t _ _) -> return $ Just $ t
_ -> return Nothing
tryToReify :: Name -> Q (Maybe Info)
tryToReify n = recover (return Nothing) (fmap Just $ reify n)
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.