This module provides type-safe access to filepath manipulations.
It is designed to be imported instead of System.FilePath. (It is intended to provide versions of functions from that module which have equivalent functionality but are more typesafe). System.Path.Directory is a companion module providing a type-safe alternative to System.Directory.
The heart of this module is the
abstract type which
represents file and directory paths. The idea is that there are
two phantom type parameters - the first should be
Path ar fd
and the second
Dir. A number of type synonyms are
provided for common types:
type AbsFile = Path Abs File type RelFile = Path Rel File type AbsDir = Path Abs Dir type RelDir = Path Rel Dir type AbsPath fd = Path Abs fd type RelPath fd = Path Rel fd type FilePath ar = Path ar File type DirPath ar = Path ar Dir
(</>) :: DirPath ar -> RelPath fd -> Path ar fd
Together this enables us to give more meaningful types to a lot of the functions, and (hopefully) catch a bunch more errors at compile time.
Overloaded string literals are supported, so with the
extension enabled, you can:
f :: FilePath ar f = "tmp" </> "someFile" <.> "ext"
If you don't want to use
OverloadedStrings, you can use the construction fns:
f :: FilePath ar f = asDirPath "tmp" </> asFilePath "someFile" <.> "ext"
f :: FilePath ar f = asPath "tmp" </> asPath "someFile" <.> "ext"
f :: FilePath ar f = asPath "tmp/someFile.ext"
One point to note is that whether one of these is interpreted as an absolute or a relative path depends on the type at which it is used:
*System.Path> f :: AbsFile /tmp/someFile.ext *System.Path> f :: RelFile tmp/someFile.ext
You will typically want to import as follows:
import Prelude hiding (FilePath) import System.Path import System.Path.Directory import System.Path.IO
The basic API (and properties satisfied) are heavily influenced by Neil Mitchell's System.FilePath module.
Ben Moseley - (c) 2009-2010