Along these lines, I also am a little foggy on unions. This: http://docs.racket-lang.org/foreign/C_Union_Types.html
says, "Unions are always treated like structs." But I have no idea what
that phrase means. I don't get the impression that unions have tags like
structs can have. Or can they? Maybe any pointer can be tagged? For example:
(define _wl_argument
(_union _int32
_uint32
_wl_fixed
_string/utf-8
(_cpointer/null 'wl_object)
_uint32
_wl_array-pointer
_int32))
Now suppose I need to pass an array of _wl_argument. Does it even make
sense to use a tag in the _cpointer?
(define _wl_argument-pointer (_cpointer 'wl_argument))
(define-wl-client wl_proxy_marshal_array_constructor
(_fun #:save-errno 'posix
_wl_proxy-pointer
_uint32
_wl_argument-pointer
_wl_interface-pointer
-> _wl_proxy-pointer/null
))
So as I said, I'm just a little foggy on some of the concepts, but I do
think the FFI is very nice. Maybe I'm just trying to use stronger typing
than actually exists in the ffi. I've started reading
Eli Barzilay/Dmitry Orlovsky "Foreign Interface for PLT Scheme".
--
Anthony Carrico
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