Stefan Behnel wrote:
> Hi,
>
> Dag Sverre Seljebotn wrote:
>> I'm thinking about letting the class author specify default buffer
>> options. Something like this:
>>
>> cdef extern class Image ...:
>> __cythonbufferdefaults__ = {'ndim' : 2}
>> __cythonbuffermandatory__ = {'dtype': unsigned char, indirect=True}
>> __cythonbufferalways__ = True
>
> I think default buffer options (mainly a default buffer layout) makes sense in
> general. It's basically saying "when I return a buffer, it will look like
> this".
>
> I wonder about the syntax, though. Wouldn't one special name + a couple of
> keyword arguments be enough?
In the discussion with Robert we kind of boiled it down to only defaults
being needed; at least mandatory has problems and does not really gain
anything. My preference now would be for __cythonbufferopts__ with a
tuple or dict giving "defaults", "mandatory" etc.
As for "being enough", in syntax discussions pretty much every syntax
proposed is possible :-) My personal taste for new syntax is this:
a) Extends the existing language grammar as little as possible
b) Won't make it harder to get "Python-runnable-Cython-code" in the future,
c) Is somewhat Pythonic (see below).
For usability these may be overriden (as with the buffer access syntax),
but this is going to be used so seldom that I don't see usability as a
concern at all -- these are going to be written once or twice per library.
Python has a long tradition of this (like __metaclass__; you and me
would have thought of all kinds of funky syntax like
class A(B, meta=C): ...
or perhaps
class A[C](B)
but Guido went with a simple __metaclass__ attribute, meaning a quite
drastical change in how the class works can be had without any new grammar.
--
Dag Sverre
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