Hi there,
I would like to use evaluate arbitrary expressions in the context of a
mixed-language (Ada, Haskell and about twelve lines of C glue)
applications. Is it possible to use dynload from hs-plugins to
load a module that references symbols in the loading program?
For example, the application contains a Haskell module that looks a bit like this:
> module TestKeys.NamedObject where
> tt :: Int
> tt = 2
I want the application to be able to offer the following sort of interaction:
haskell> tt
2
haskell>
But what actually happens is this:
haskell> tt
test_haskell3: /tmp/MDnum15633.o: unknown symbol `TestKeysziNamedObject_tt_closure'
test_haskell3: user error (resolveObjs failed with <<False>>)
Compiling Haskell code in advance works (i.e. if I create and compile a
module that evalutes tt and link it in, everything runs fine).
This is how I try to evaluate the expression:
> evaluate :: String -> IO ()
> evaluate "" = return ()
> evaluate e = do writeFile "temp.hs" fileContents
> status <- makeWith "LeanderStub.hs" "temp.hs" ["-c"]
> case status of MakeSuccess code path -> loadAndEval path
>
MakeFailure
error -> print error
> where fileContents = "module Temp where\n\
>
\ result = " ++ e ++ "\n"
>
> loadAndEval :: FilePath -> IO ()
> loadAndEval path = do mv <- dynload path [] [] "result"
> case mv of
>
LoadFailure msg -> print msg
> LoadSuccess _ v -> putStrLn v
LeanderStub.hs is a module containing the necessary imports for the expression to evaluate in the right context.
I was hoping that passing "-c" to makeWith would create an object file
whose missing dependencies would be resolved when it was loaded into an
application which contained them. Is this a dumb
expectation? The alternative -- linking to the entire application
for each expression evaluated -- seems a bit over the top, and I can't
see how state would be maintained.
I originally used unsafeEval_, but this has the same problem.
I can't help but think that this must have been done before. Any
advice? If you know Guile, then the equivalent of gh_repl is what
I'm really after.
cheers,
Fraser.