filepather

Re-implementations of System.FilePath and System.Directory using Kleisli type aliases from the kleisli package.

Each function that takes a FilePath as its subject argument is expressed as a Kleisli value, enabling composition via Functor, Applicative, Monad, and other type class instances.

Modules

Type aliases

type FilePather  p f a = Kleisli p FilePath f a
type FilePather' p a   = FilePather p Identity a
type FilePatherA f a   = FilePather (->) f a
type FilePatherA' a    = FilePatherA Identity a

Usage

import System.FilePather
import Data.Kleisli (Kleisli(..))
import Data.Functor.Identity (runIdentity)

-- Pure operations return FilePatherA' (Kleisli (->) FilePath Identity a)
-- >>> runIdentity (let Kleisli f = takeExtension in f "/foo/bar.hs")
-- ".hs"

-- Effectful operations return FilePatherA IO a (Kleisli (->) FilePath IO a)
-- >>> let Kleisli f = doesFileExist in f "/tmp/example.txt"
-- False

-- Partial operations return FilePatherA Maybe a
-- >>> let Kleisli f = stripExtension ".hs" in f "/foo/bar.hs"
-- Just "/foo/bar"

-- Compose with Functor/Applicative/Monad instances
-- >>> runIdentity (let Kleisli f = fmap (++ ".bak") takeFileName in f "/tmp/notes.txt")
-- "notes.txt.bak"

Building

cabal build
cabal test doctest
cabal bench