FFI Definition

[Marcin 'Qrczak' Kowalczyk]

Sun, 6 May 2001 11:29:18 -0600 (MDT), Alastair Reid <reid at cs.utah.edu> pisze:

>> foreign export dynamic is a shortcut for importing an automatically
>> generated nontrivial C function, with argument type not conforming to
>> regular imports, which could not be written by hand. 
> 
> I don't get it.  How do you use a function with a type like:
> 
>   (Int -> IO Int) -> Addr
> 
> to import a C function?

*This* is an imported function.

Well, if I wanted to make it by hand, I would have to make a StablePtr
before, because I can't pass (Int -> IO Int) to a foreign function
directly.

In other words
    foreign export dynamic exp :: (Int -> IO Int) -> IO Addr
is equivalent to
    exp :: (Int -> IO Int) -> Addr
    exp f = exp' =<< newStablePtr f
    
    foreign import exp' :: StablePtr (Int -> IO Int) -> IO Addr
    -- exp' generated by the Haskell compiler.

> Unless you're arguing that, since it brings a name into scope it
> can be thought of as a kind of import??? (But I don't think you
> are saying that.)

I am!

-- 
 __("<  Marcin Kowalczyk * qrczak at knm.org.pl http://qrczak.ids.net.pl/
 \__/
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QRCZAK