[Cython] Utility Codes and templates

[mark florisson]

On 23 July 2011 09:37, Stefan Behnel <stefan_ml at behnel.de> wrote:
> Robert Bradshaw, 22.07.2011 23:44:
>>
>> 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.
>
> It's unlikely to be useful for the ctypes backend, but C/C++ will benefit
> from it, and so may others.
>
>
>>>>> 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 ##############
>
> Hmm, right. Cython utility code doesn't actually need any separate parts. I
> hadn't realised that.
>
> +1, the above is well visible and doesn't hurt the file syntax.
>
>
>>> 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.
>
> -1, I see no reason to do it the wrong way now only to clean it up later.
> Why not just do it right? It's not like that's so much more work. I can help
> out.
>
>
>> 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.
>
> Requiring a short declaration at the top of the file makes it easier to find
> out what's in that file from a quick look at the top, rather than having to
> skip (or grep) through it. Yes, I think it makes sense to put this into some
> kind of file header.
>
> Coming back to my ini file proposal, what about a file syntax like this:
>
>
> /*
> [MyUtil1]
> requires = file1:abc
>
> [MyUtil2]
> ; nothing to declare ...  (I think it's ; for comments - don't care)
> */
>
> ///////////////// MyUtil1.proto /////////////////////
> ...
>
>
> and the same for Cython code:
>
> """
> [MyUtil1]
> requires = file1:abc
>
> [MyUtil2]
> requires = MyUtil1
> """
>
> ################### MyUtil1 #####################
> ...
>
> The initial section is trivial to extract and to drop into RawConfigParser,
> and we are completely free to extend the metadata section later on, without
> having to touch the code as well.
>

Looks good to me. Up to now you could also use comments at the top but
they were just dropped.

>>>> 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)
>
> Yes, it's clearly a problem in Cython code. It would work very nicely for C
> code, though. I think we should use it there right from the start.
>

I concur that the {{ }} can show up like an ugly red in some
situations. I do think comments are nicer. However for Cython
templates you'd have to use triple-quoted strings in order to get a
benefit (I assume you occasionally want something that stretches
multiple lines).

>>>> 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'm fine with {{ }} for Cython code. It's just as good as anything else.
>
>
>>> I'll add tempita to Cython.
>>
>> Sounds good. (If anyone else has objections, bring them up now...)
>
> Tempita is fine with me.
>
> Stefan
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