On Jul 31, 2008, at 1:07 AM, Dag Sverre Seljebotn wrote:
> 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.
I am for keeping it very simple, so I would propose a single
dictionary __cythonbufferdefaults__.
> 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).
A counter-argument is that if you misspell it, it will silently fail
to work. (You still have me convinced though.)
> 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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