[Cython] Declaration syntax change

[Stefan Behnel]

Nathaniel Smith, 03.10.2013 14:35:
> On Thu, Oct 3, 2013 at 1:23 PM, Stefan Behnel wrote:
>> Greg Ewing, 03.10.2013 14:10:
>>> Robert Bradshaw wrote:
>>>>     cdef int *a, b, c, *d[3]
>>>>
>>>> is IMHO quite ugly but also adds a lot of complexity to the parser.
>>>> What if instead we required
>>>>
>>>>     cdef int* a
>>>>     cdef int b, c
>>>>     cdef int[3]* d
>>
>> The last line looks ambiguous, BTW, hadn't even noticed it before. Is that
>> an array of int pointers or a pointer to an array (pointer)? We should make
>> sure the way this is declared is really obvious and not unexpected to C users.
> [...]
> The two halves of this email seem to sort of contradict each other,
> don't you think? At least the C syntax has the advantage that it's
> well-defined and many people *do* know it (and if they don't then
> there are bazillions of references around, plus you can just copy it
> out of header files if you're wrapping a C library), whereas as noted
> above, in fact there are *no* people who know how to look at int[3]*
> and be confident about what it means, even you...?

Well, it's still better than looking at "*d[3]", now, isn't it? Maybe I'm
just confused (by both, actually) because I'm not really breathing C.

If the following is what it's supposed to mean, then I find it quite
straight forward, and more obvious than the C spelling:

    cdef int* a       # pointer to int
    cdef int[3]* b    # pointer to 3-item int array
    cdef int*[3] c    # 3-item array of pointers to int

I agree that the argument of "copying it out of a header file" has a
certain value, although pointer declarations are not exactly the most
common thing to find in header files. We shouldn't make it *harder* to copy
things from header files, though, because it's already a drawback of Cython
that you have to do that at all.

Stefan