> -----Original Message-----
> From: Alastair Reid [mailto:reid@reid-consulting-uk.ltd.uk]
> Sent: 02 July 2002 18:34
> To: Ian Lynagh
> Cc: ffi(a)haskell.org
> Subject: Re: More C interfacing issues
>
>
>
> > Firstly, some ncurses calls return a *WINDOW and others take one as
> > an argument but you never actually look at the contents of one
> > yourself. I have defined "data Window = Window" and am using Ptr
> > Window for the types of these. However, this means I get a warning
> > about an unused constructor. Is there a better way to do this?
>
> Hugs supports:
>
> data Window
>
> and I believe GHC and NHC do too. (Malcolm, SimonM: please
> shout if I overstate.)
Yes, GHC does.
>
> > Secondly, does anyone have any suggestions on how to provide an
> > interface to this?
>
> > void getyx(WINDOW *win, int y, int x);
>
> > The getyx macro places the current cursor position of the given
> > window in the two integer variables y and x.
>
> > The type would probably ideally be "Ptr Window -> IO (CInt, CInt)".
>
> The easy way is to use GreenCard (the other ffi frontends may be of
> use too).
>
> Or, you can do what GreenCard does which is to add 3 wrapper functions
> more or less like this:
What's wrong with just doing this in the plain FFI?
data Window
foreign import ccall "getyx"
getyx :: Ptr Window -> Ptr CInt -> Ptr CInt -> IO ()
niceGetYX :: Ptr Window -> IO (CInt, CInt)
niceGetYX win =
alloca $ \py ->
alloca $ \px -> do
getyx win py px
y <- peek py
x <- peek px
return (x,y)
Have I missed something?
Cheers,
Simon
