[Cython] Declaration syntax change

[Chuck Blake]

Greg Ewing wrote:
>What would be the benefit of this? You're proposing to change
>from something identical to C declaration syntax, which is
>second nature for a great many people, to something that
>looks deceptively like C syntax but isn't.
>
>I can't see that causing anything other than a massive
>amount of confusion, anguish and hair-tearing.

I would echo this, actually.  While the C declarator syntax takes
a while to get used to, there is actually a simple rationale for
why it is the way it is: just one set of operator associativity
and precedences.  The way [], *, and function call ()s bind do
not vary by context.  One doesn't have to remember multiple sets
of rules "tailored" for various contexts like declaration/typedef
definition or casting vs operator application.

I believe this is the "fact underlying" the reactions various folk
here are having of "initially seemingly clearer, but oh wait..what
about corner case?"  There is a simplicity embedded in the seemingly
backwards "operators you need to apply to get the base type" rule.

The manual translation of C headers/decls to Cython is another good
point.  I think that it's a big departure from the perhaps hard to
articulate "sweet spot" Cython/Pyrex are trying to hit straddling
the C & Python worlds.


Stefan Behnel wrote:
>Also, C is only second nature to some people. A great many people actually
>use Cython specifically to *avoid* having to write C.

This is a fair point, but Pyrex/Cython have a decade plus long
history here of being very close to C in this specific way,
which is kind of a central thing..almost like a different way
to spell the same type grammar.  It's easy after a short while
to visually see the translation.  With whole new syntax and maybe
parens in new, shiner places, I doubt seeing the mapping would be
so easy for "hard cases".  And easy cases are easy.


On a separate relase-number-tying note, I also feel like the
Cython 1.0 target (or even Pyrex 1.0) was always more about
compatibility with "whatever Python you throw at the Cython
compiler" than about finality to all the various extended
Cython syntax areas.  There are quite a few beyond-Py syntax
areas at this point.

So, *if* the conclusion is that there is a group will and solid
rationale to let Cython allow a user to use an *alternate* type
declaration sub-language/warnings/a wrapper/macro syntax, then I
don't see any 1.0-release relevance.  Cython grows just yet another
way to specify the same things at whatever rev is easy.  The 1.0
only matters if it's a strict backward incompatible proposal,
but I sense a bit of discord on this response chain about that.
Maybe changing "cdef" to be "cydef" would be a visual flag that
an entirely different syntax is afoot?  But then..sooo many ways
to specify types.

If you really want to be *that* different - arguably almost as
much as different as simply requiring Python3 and annotations
rather than having "cdef" at all, then why not go all the way
and full on require Py3?  Then a user confronts all the Py3 core
syntax change and Cy2.0 (or maybe Cy1.5 as 3.0/2 or whatever)
at the same time.  And, why, the changes are even related to
only-in-Py3 things to boot.  Just my two cents, anyway.

cb