Thu, 17 Aug 2000 18:53:04 +1000, Manuel M. T. Chakravarty <[EMAIL PROTECTED]> pisze:
> > foreignObjToPtr :: (Ptr a -> IO b) -> ForeignObj -> IO b
> * Shouldn't we use
>
> foreignObjToPtr :: ForeignObj -> (Ptr a -> IO b) -> IO b
Maybe. I considered this too and generally cannot decide myself in
such cases, where function can be second because it's usually larger,
but putting it first creates a "function transformer".
The former type gives IMHO better order in case the peeking functions
is short - the same order as it would be with pointers:
fileOwner:: FileStatus -> UserID
fileOwner (FS obj) = unsafePerformIO $
foreignObjToPtr (#peek struct stat, st_uid) obj
BTW, I use your order in
ptrTo :: Storable a => a -> (Ptr a -> IO b) -> IO b
but the reverse in convertArg method (which often = id), and thus
instance Storable a => ForeignArg (Ptr a) a where
convertArg f x = ptrTo x f
I'll switch the argument order. IMHO it should be called openForeignObj
or withForeignObj; aToB suggests the type A -> B.
"touch:: ForeignObj -> IO ()" is the primitive needed for that.
In current ghc NOINLINEd "\_ -> return ()" on ForeignObj# is the best
implementation known to me, but a primop would be more efficient.
> * Does GHC usually do inlining here?
In my experiments yes. fileOwner is compiled to nested STG cases.
ConvertArg class uses a higher order function for each argument
and GHC nicely optimizes their calls (and overloading) away, except
big functions.
------------------------------------------------------------------------
PS. I've added to glue-hsc automatic generation of C files + headers
(with right #includes in .hs, .h and .c) that contain hand-written
wrappers. Example:
foreign import "getErrno" unsafe errno :: IO CInt
#wrapper int getErrno (void) {return errno;}
C wrappers are needed for non-constant macros.
--
__("< Marcin Kowalczyk * [EMAIL PROTECTED] http://qrczak.ids.net.pl/
\__/
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