Haskell and symbolic references
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? Thanks a lot, Patrick Leboutillier -- ===================== Patrick LeBoutillier Rosemère, Québec, Canada
From: haskell-cafe-bounces@haskell.org [mailto:haskell-cafe-bounces@haskell.org] On Behalf Of 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?
Dynamic loading via plugins will do this. It was broken on Windows for some time; not sure if it works there now. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/plugins Alistair ***************************************************************** Confidentiality Note: The information contained in this message, and any attachments, may contain confidential and/or privileged material. It is intended solely for the person(s) or entity to which it is addressed. Any review, retransmission, dissemination, or taking of any action in reliance upon this information by persons or entities other than the intended recipient(s) is prohibited. If you received this in error, please contact the sender and delete the material from any computer. *****************************************************************
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]
You could use Data.Map: call_func = (funcMap !) where funcMap = fromList [ ("add", add) , ("sub", sub) , ("mul", mul) , ("div", div)] Or a version using lookup instead of (!) if you aren't sure that the string will be a valid function name. - Jake
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
(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
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
participants (5)
-
Bayley, Alistair -
Jake McArthur -
Khudyakov Alexey -
Matt Morrow -
Patrick LeBoutillier