[Cython] Utility Codes and templates

[Dag Sverre Seljebotn]

On 07/22/2011 06:04 PM, Stefan Behnel wrote:
> Dag Sverre Seljebotn, 22.07.2011 17:49:
>> On 07/22/2011 05:46 PM, Dag Sverre Seljebotn wrote:
>>> On 07/22/2011 03:07 PM, Stefan Behnel wrote:
>>>> Stefan Behnel, 22.07.2011 15:04:
>>>>> Dag Sverre Seljebotn, 22.07.2011 13:54:
>>>>>> On 07/22/2011 01:10 PM, Stefan Behnel wrote:
>>>>>>> I'm fine with using a template engine for the more involved cases
>>>>>>> (which
>>>>>>> are rare enough). However, I'd prefer not adding a new
>>>>>>> dependency, but
>>>>>>> just shipping a tiny single-module engine with Cython, e.g.
>>>>>>> Templite or
>>>>>>> pyratemp (just found them, never used them).
>>>>>>
>>>>>> BTW, I don't think anybody is suggesting having an *external*
>>>>>> dependency
>>>>>> that users would need to go fetch themselves....that would be insane.
>>>>>
>>>>> Sure. I also don't mind having a small engine in a package, but just
>>>>> putting a single file in the source tree (and overwriting it with a
>>>>> new
>>>>> version at need) would be a perfectly small and nonintrusive addition.
>>>>> And
>>>>> given that there really are engines of that size (one file, <500
>>>>> lines),
>>>>> it's not so unrealistic either.
>>>>>
>>>>> That being said, if you can recommend Tempita (which IMHO qualifies as
>>>>> "small enough"), I won't object to it.
>>>>
>>>> ... although, isn't it unfortunate that it uses "{{...}}" for template
>>>> code? How well readable is that when used in C code?
>>>
>>> At least in emacs, pretty much any template syntax will mess up things
>>> pretty badly, especially automatic indentation and so on.
>>>
>>> What I do is using mmm-mode, so that everything within {{ and }} is
>>> highlighted with python-mode, and the rest with c-mode. I'll share my
>>> configuration later.
>>>
>>> I'm merely stating why this has never been an issue for me, I'm NOT
>>> suggesting everyone should use emacs (or that plain text editing isn't
>>> convenient); you do have a point.
>>>
>>> Keep in mind that a syntax must work well with utility code written in
>>> Cython as well.
>>
>> OTOH one *might* want to have
>>
>> code.put_tempita(..) # or similar
>>
>> in Python code, and in that case plain text readability is very
>> important.
>>
>> Of course, hacking Tempita to make it %[ ]% instead is a five minute job.
>> But I'm happy with any other engine that somebody have actually tried out
>> extensively.
>
> Tempita has a syntax for comments - what about using the regular C and
> Cython comments as template syntax delimiters? That way, you'd write
>
> /*# some comment */
>
> to get an actual comment in C code, and
>
> /* for x in y */
>
> for template code. For Cython code, we could use "##", or maybe "#<" and
> ">#". That should work pretty well with editors.

I really like the idea of making use of comments, but I don't think we 
should "overload" the C comments; both for human parsing and because it 
is helpful with comments in generated Cython code as well (at least I 
would like to see much more of that!)

For Cython code, this doesn't work well for inline expressions:

variable#<idx># = 34

So I propose

C: /*$  $*/

Cython: "$  $"

Or some other character than $ that we can have in common between C and 
Cython (! is taken by documentation systems, but : is an option...).

Using a string in Cython should play better with at least some syntax 
highlighters, and we can simply make sure to use ' for all actual strings.

Dag Sverre