[Cython] Utility Codes and templates

[Vitja Makarov]

2011/7/23 Robert Bradshaw <robertwb at math.washington.edu>:
> On Fri, Jul 22, 2011 at 1:39 PM, mark florisson
> <markflorisson88 at gmail.com> wrote:
>> On 22 July 2011 22:05, Robert Bradshaw <robertwb at math.washington.edu> wrote:
>>> On Fri, Jul 22, 2011 at 3:12 AM, mark florisson
>>> <markflorisson88 at gmail.com> wrote:
>>>> For my work on the _memview branch (and also on fused types) I noticed
>>>> that UtilityCodes started weighing heavily on me in their current
>>>> form, so I wrote a little loader in the _memview branch:
>>>>
>>>> https://github.com/markflorisson88/cython/commit/e13debed2db78680ec0bd8c343433a2b73bd5e64#L2R110
>>>>
>>>> The idea is simple: you put your utility codes in Cython/Utility in
>>>> .pyx, .c, .h files etc, and then load them. It works for both
>>>> prototypes and implementations, for UtilityCode and CythonUtilityCode:
>>>
>>> This sounds like it could be a nice way to organize our UtilityCode
>>> snippets. So far we haven't really needed any more templating than
>>> simple substitution, but for what you're doing I can see this being
>>> quite handy. This may also provide a more flexible way forward for
>>> supporting multiple backends.
>>>
>>>> myutility.c
>>>>
>>>> // UtilityProto: MyUtility
>>>> header code here
>>>>
>>>> // UtilityCode: MyUtility
>>>> implementation code here
>>>>
>>>> You can add as many other utilities as you like to the same file. You
>>>> can then load it using
>>>>
>>>>    UtilityCode.load_utility_from_file("myutility.c", "MyUtility")
>>>
>>> I agree with you that having multiple related, named snippets in same
>>> file is worthwhile. What about
>>>
>>> ////////////////////// MyUtility.proto ///////////////////////////
>>>
>>> and
>>>
>>> ############ MyCyUtility ##############
>>>
>>> so the chunks are easy to see.
>>
>> Sounds like a good idea. How would we handle the requires list in that
>> case though? Or should we leave that to the Python code that loads it
>> for now?
>
> For now, lets leave them with the Python code. Eventually we could do
> something similar to how we do Cython pragmas, i.e. parse the comments
> that occur at the top of the file (chunk) as having special meaning.
>
>>>> Of course you can pass in any other arguments, like proto_block, name,
>>>> etc. You can additionally pass it a dict for formatting (for both the
>>>> prototypes and the implementation). It will return a UtilityCode
>>>> instance ready for use.
>>>> You can also simply retrieve a utility code as a string, where it
>>>> returns (proto, implementation).
>>>>
>>>> As debated before, an actual template library would be really
>>>> convenient. Dag and I had a discussion about it and he suggested
>>>> Tempita (by Ian Bicking), it is compatible with Python 2 and Python 3,
>>>> and is pure-python. It supports all the good things like iteration,
>>>> template inheritance, etc. Now I'm not sure whether it supports python
>>>> 2.3 as it doesn't compile on my system, but it does support 2.4
>>>> (confirmation for 2.3 would be appreciated). On a side note, I'd be
>>>> perfectly happy to drop support for 2.3, it's kind of a chore.
>>>> The documentation for Tempita can be found here: http://pythonpaste.org/tempita/
>>>
>>> Looks like a reasonable choice to me, it's small enough to ship and
>>> looks versatile enough to do everything we need. There's certainly not
>>> a shortage of options, but I'm happy with your and Dag's endorsement.
>>>
>>> In terms of delimiters, I prefer some form of strings over comments
>>> (often a value is expected, and Python's comments always extend to the
>>> line break) but sticking with the {{ }} syntax appeals to me even
>>> more. It's pretty standard, and decent syntax hilighters shouldn't
>>> choke on it (well, the surrounding code) too bad.
>>
>> Ok, that's fine with me. It would be easily changeable if we revert
>> later anyways.
>
> Yep, which makes it a much easier decision than trying to figure out a
> templating solution for the user-visible front-end.
>
>> I'll add tempita to Cython.
>
> Sounds good. (If anyone else has objections, bring them up now...)
>

Tempita looks cool, +1

-- 
vitja.