[Haskell-cafe] another FFI question

[Galchin, Vasili]

On Sat, Jun 21, 2008 at 1:28 PM, Ryan Ingram <ryani.spam at gmail.com> 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 <vigalchin at gmail.com>:
> > 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 at 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 at gmail.com
> >>
> >
> >
> > _______________________________________________
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> > http://www.haskell.org/mailman/listinfo/haskell-cafe
> >
> >
>
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