"Sigbjorn Finne (Intl Vendor)" <[EMAIL PROTECTED]> wrote,
> > Sven Panne [mailto:[EMAIL PROTECTED]] writes:
> >
> > "Sigbjorn Finne (Intl Vendor)" wrote:
> > > Sven Panne wrote:
> > > > What's wrong with using Green Card? Its %enum generates
> > > > the desired mappings automatically and consistently. AFAIK,
> > > > this type safety is something even IDL compilers don't do
> > > > for you.
> > >
> > > Use whatever works best for you, but I'm not sure I agree with this
> > > statement re: enums. Care to expand? :)
> >
[...]
> >
> > And here in Green Card:
> >
> > -- Bar.gc -----------------------------------------------
> > module Bar where
> >
> > import StdDIS
> > import Word
> >
> > %enum Status Int [ EXIT_FAILURE, EXIT_SUCCESS ]
> > %fun exit :: Status -> IO ()
> >
> > %enum Whence Int [ SEEK_SET, SEEK_CUR, SEEK_END ]
> >
> > newtype Offset = Offset Word32;
> > %dis offset x = Offset (word32 x)
> >
> > newtype Fd = Fd Int;
> > %dis fd x = Fd (int x)
> >
> > %fun lseek :: Fd -> Offset -> Whence -> IO Offset
> > ---------------------------------------------------------
> >
>
> You could use 'const's for this, but I'd suggest using an
> 'enum' decl in IDL instead. IDL 'enum' declarations are just
> like in C, but HDirect extends 'em a little by supporting
> the custom 'deriving()' attribute. For example,
>
> typedef [deriving("Eq")]
> enum { EXIT_FAILURE = 0, EXIT_SUCCESS } Status;
>
> gives
>
> data Status = EXIT_FAILURE | EXIT_SUCCESS
>
> instance Eq Status where {...}
> instance Enum Status where {...}
>
> which should be equal in power to %enum.
Isn't there still a difference? When the C-library changes
(ie, you get a new version) and the definition of `Status'
changes to
enum Status {
EXIT_FAILURE = -1;
EXIT_SUCCESS = 0;
}
The IDL binding would produce wrong code, but the Green Card
binding would still be correct. Right? Or do I miss
something?
Manuel
