Re: [Haskell-cafe] Haskell and symbolic references

(i always forget to reply-to-all) If you'd like to reference C functions with Strings, one possible way is to use System.Posix.DynamicLinker and the wrapper over libffi that's been uploaded to hackage recently: [m@monire asdf]$ ghci GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. ghci> :m + Foreign.LibFFI ghci> :m + Foreign.Ptr Foreign.Storable ghci> :m + Foreign.C.Types Foreign.C.String ghci> :m + System.Posix.DynamicLinker ghci> malloc <- dlsym Default "malloc" Loading package unix-2.3.1.0 ... linking ... done. ghci> syscall <- dlsym Default "syscall" ghci> :! echo -ne "#include \n__NR_execve\n" | cpp | tac | grep -E "^[0-9]+$" | head -1 > NOODLES ghci> nr_execve :: CLong <- (read . head . words) `fmap` readFile "NOODLES" ghci> :! rm -f NOODLES ghci> let sizeOfPtrCChar = sizeOf(undefined::Ptr()) ghci> argv <- callFFI malloc (retPtr (retPtr retCChar)) [argCSize (2*fromIntegral sizeOfPtrCChar)] Loading package bytestring-0.9.1.4 ... linking ... done. Loading package libffi-0.1 ... linking ... done. ghci> sh <- newCString "/bin/sh" ghci> poke argv sh ghci> poke (argv`plusPtr`sizeOfPtrCChar) 0 ghci> callFFI syscall retCLong [argCLong nr_execve, argPtr sh, argPtr argv, argCInt 0] {-never returns-} sh-3.2$ echo $0 /bin/sh sh-3.2$ exit exit [m@monire asdf]$ Matt On Fri, May 29, 2009 at 11:41 AM, Khudyakov Alexey < alexey.skladnoy@gmail.com> wrote:

On Friday 29 of May 2009 19:34:44 Patrick LeBoutillier wrote:

...

Hi all,

Is it possible with Haskell to call a function whose name is contained in a String? Something like:

five = call_func "add" [2, 3]

If not, perhaps this is acheivable using FFI?

Or maybe you are asking for template haskell[1]. With it you can actually generate function at compile time. It depends on waht you actually need.

...

{-# LANGUAGE TemplateHaskell #-} import Language.Haskell.TH

five = $( foldl appE (varE $ mkName "+") [ litE $ integerL 2 , litE $ integerL 3 ] )

[1] http://haskell.org/haskellwiki/Template_Haskell

-- Khudyakov Alexey _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe