On Mon, Feb 06, 2006 at 12:08:12PM +0300, Bulat Ziganshin wrote:
Hello Einar,
Saturday, February 04, 2006, 12:00:18 AM, you wrote:
KA> * Do you think that we have to use unboxed arrays of Word8/Word16 KA> for file path?
well, if FilePath should be ADT, then:
1) all operations that returns filenames (getFileContents, anything more?) should return this ADT instead
I agree. In System.Directory: You mean getDirectoryContents? getCurrentDirectory, getHomeDirectory, getTemporaryDirectory, etc. canonicalizePath. All sorts of Cabal stuff. Some of these could just return String. Others could return the ADT... Actually couldn't they all be made polymorphic? getDirectoryContents :: FilePath p => IO p class FilePath p where fromADT :: ADT -> p toADT :: p -> ADT (where I have declined naming the ADT)
2) this ADT should support conversion to/from String (for interaction with users) and to/from [Word8] (to send these values across storage/network). Of course, these conversions should be as exact and revertible as possible, i think that at least we can make guarantee for ascii chars
Probably we'd also want a withCString equivalent that works with the ADT, for use when working with the FFI. True, you could do the conversion via [Word8], but that's ugly (and potentially inefficient, depending how the ADT is stored internally).
3) all operations that receives filenames should accept a _class_ which includes String/[Word8]/this ADT
That would be nice, but I suspect not strictly necessary.
of course, this means incompatible changes in the APIs, so it's better to introduce new fucntions that returns ADT/accepts class with a new names
I don't know. I'd lean towards not introducing new function names. The point of accepting the class would be that existing code would continue to work. The only code that would be broken would be code that uses getFileContents, which is a sufficiently small minority of code that I would say just let it break. You'd leave the Haskell 98 Directory module returning String, but I'd vote to make System.Directory. -- David Roundy http://www.darcs.net