compile-time regex redux

[kenny]

BCS wrote:
> Walter Bright wrote:
>> kenny wrote:
>>
>>> I know I'm asking for a lot, but the way templates handle string are 
>>> still kinda weird to me. Would string parsing in this sort of way be 
>>> absolutely impossible with templates? I have not had good luck with it. 
>>
>>
>> I just haven't thought about this enough. Certainly, however, solving 
>> the problem in a more general, D-ish way than regex would be a much 
>> bigger win. Regex works only for a subset of problems (can't do 
>> recursive descent parsing with it).
> 
> As I see it the biggest problem with compile time parsing in D is that 
> building non linear structure is a pain. Tuples implicitly cated when 
> passed together an this make some things really hard. Allowing a tuple 
> to be a member of another tuple would put D template in the same class 
> as LISP.
> 
> Another things that might make things easier is some way to mark a 
> template as "evaluate to value and abandon". This would cause the 
> template to be processed but none of the symbols generated by it would 
> be kept, only the value. Of course, suitable restrictions would apply.

so it would be like writing normal D code inside of a template? Could we use phobos or do more metastring functions like find, strip, etc. need to be reinvented in D. Or can I take those functions and just put a wrapper around it? I think this is getting into the security issues again, but something like this:

auto my_text = meta trim_whitespace(import("myxml.xml")); // obviously a better keyword should be used, and can only be used in global scope too.

where trim_whitespace is an actual function that is actually defined up in the file somewhere, and will be compiled, used on the import file, then discarded and the result stored into auto my_text? A day or so ago, someone mentioned a .rc compiler. I personally would use it to parse stuff for interface elements .. to generate them dynamically. We already have libraries to parse XML (XHTML), CSS, and other config type things. It would be SUPER AWESOME to be able to just re-use them as a template without any other extra work!!! Oh man, that has me really excited, if that's possible :)

woah!