On Friday 13 June 2003 3:37 am, Matthew Donadio wrote:
Hi all,
I have a couple of questions about Green Card and exceptions.
[...]
This definition works, but it ignores the return code from the library function. The various return codes are from an enum defined in a header file. I would like to throw a Haskell exception (one of the ArithExceptions defined in Control.Exception) depending on the value of "rc".
The %fail statements (described in the last few paragraphs of http://www.haskell.org/greencard/downloads/greencard-latest/type-sig.html) consist of two C expressions. For example: %fail {f == NULL} {errstring(errno)} The first is a test for failure. The second is an expression which returns a C string. If the test expression fails, the string expression is evaluated and used to generate a UserError.
If I have to create a DIS, can this be shared across several modules that all need the same functionality?
It would be nice to be able to write something like: %fail POSIX_FD(fd) where POSIX_FD is something you defined elsewhere (e.g., it might test if its file-descriptor argument is -1). GreenCard can't do this. It would also be nice to be able to generate a different error instead of UserError. We'd need to specify the type and the exception constructor so a plausible syntax would be: %fail {f == NULL} (UserError (string {errstring(errno)})) [Detail: should it be a Haskell98 IOError constructor or a non-standard but widely implemented exception constructor? Should it be a function or a constuctor?] Again, GreenCard can't do that. As GreenCard maintainer, I've got to ask: - How many users of GreenCard are still out there? - Are you developing new libraries or just maintaining the ones you've got? - Is there a demand for new features? -- Alastair Reid