AppendFile.hs

Class.hs

{-# LANGUAGE FlexibleInstances    #-}
{-# LANGUAGE TypeFamilies         #-}
{-# LANGUAGE TypeSynonymInstances #-}

module Path.Class
    (AppendFile)
    where

import           Path            (Dir, File, Path, Rel)
import qualified Path            as Path
import           System.FilePath (FilePath)
import qualified System.FilePath as FilePath


class AppendFile d where
    type FileName d :: *
    type Result d :: *
    (</#>) :: d -> FileName d -> Result d

instance AppendFile FilePath where
    type FileName FilePath = FilePath
    type Result FilePath = FilePath
    (</#>) = (FilePath.</>)

instance AppendFile (Path b Dir) where
    type FileName (Path b Dir) = Path Rel File
    type Result (Path b Dir) = Path b File
    (</#>) = (Path.</>)

ClassWithMaybe.hs

{-# LANGUAGE FlexibleInstances    #-}
{-# LANGUAGE TypeFamilies         #-}
{-# LANGUAGE TypeSynonymInstances #-}

module Path.ClassWithMaybe
    (AppendFile)
    where

import           Control.Monad
import           Path            (Dir, File, Path, Rel)
import qualified Path            as Path
import           System.FilePath (FilePath)
import qualified System.FilePath as FilePath


class AppendFile d where
    type FileName d :: *
    type Result d :: *
    (</#>) :: d -> FileName d -> Result d

instance AppendFile FilePath where
    type FileName FilePath = FilePath
    type Result FilePath = Maybe FilePath
    dir </#> file = do
        guard $ FilePath.isRelative file
        return $ dir FilePath.</> file

instance AppendFile (Path b Dir) where
    type FileName (Path b Dir) = Path Rel File
    type Result (Path b Dir) = Path b File
    (</#>) = (Path.</>)