Ross Paterson <[EMAIL PROTECTED]> wrote, > On Sun, Jun 08, 2003 at 09:06:07PM +1000, Manuel M T Chakravarty wrote: > > Ross Paterson <[EMAIL PROTECTED]> wrote, > > > On Wed, Jun 04, 2003 at 11:09:43PM +1000, Manuel M T Chakravarty wrote: > > > > StablePtr are used to export references to Haskell values to > > > > C, where they are treated as abstract data. In C one > > > > traditionally uses (void *) for that purpose (see "man > > > > qsort(3)"). We want to make sure HsStablePtr is not to wide > > > > to be passed as an argument to C functions expecting such > > > > abstract types (such as qsort(3)). > > > > > > How does HsStablePtr differ from HsDouble in this respect? > > > (except that the C side can do even less with > > > HsStablePtr.) > > > > HsDouble is guaranteed to be one of C's floating types; > > hence, all operations on floating types can be applied on > > values of type HsDouble. > > I meant to say that you can't pass an HsDouble to a "polymorphic" C > function expecting (void *), so why should you be able to pass an > HsStablePtr?
Because HsStablePtr (in contrast to HsDouble) is used to pass abstract Haskell values to C routines, so that they can pass them around, store them, and pass them back to Haskell. C routines that are meant to handle abstract values usually use (void *). Manuel _______________________________________________ FFI mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/ffi