Re: [Haskell-cafe] another FFI question

On Sat, Jun 21, 2008 at 1:28 PM, Ryan Ingram wrote:

You just have the arguments to "poke" wrong: poke :: Storable a => Ptr a -> a -> IO ()

So you are missing the pointer argument poke p Signal = poke p signal_int_value

^^ what is "signal_int_value"?

I didn't know about the (#const) syntax. Interesting.

Also, alignment of signal should match the alignment of the underlying type (although I think that isn't really used at the moment).

-- ryan

2008/6/20 Galchin, Vasili :

...

I am still reading the web pages. Here is what I tried:

data SigNotify = Signal | None | Thread | ThreadId

instance Storable SigNotify where

sizeOf _ = (#const sizeof (int))

alignment _ = 1

poke Signal = (#const SIGEV_SIGNAL)

poke None = poke (#const SIGEV_NONE)

poke Thread = poke (#const SIGEV_THREAD)

poke ThreadId = poke (#const SIGEV_THREAD_ID)

but I got ...

Couldn't match expected type `Ptr SigNotify' against inferred type `SigNotify' In the pattern: Signal In the definition of `poke': poke Signal = poke (0) In the definition for method `poke'

Basically I want to marshall SigInfo constructors to CInt values. ??

Regards, Vasili

On Fri, Jun 20, 2008 at 3:20 PM, Bulat Ziganshin < bulat.ziganshin@gmail.com> wrote:

...

Hello Vasili,

Friday, June 20, 2008, 11:51:11 PM, you wrote:

...

data Bonzo = A | B |C

...

How do I write the poke functions and call them?

instance Storable Bonzo poke A = poke 0 poke B = poke 1 poke C = poke 4

call as "poke x"

probably, you don't understand differences between OOP classes and type classes. look at

http://haskell.org/haskellwiki/OOP_vs_type_classes

...

and papers mentioned there

-- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com

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