[petsc-dev] Documentation comment support

[Matthew Knepley]

On Wed, Jan 9, 2013 at 7:58 AM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> On Tue, Jan 8, 2013 at 10:35 PM, Matthew Knepley <knepley at gmail.com>wrote:
>
>> Look at the grammar from the back of K&R. It requires TYPE tokens when
>> you have definitions. However,
>> the lexer will produce an ID token unless you look it up in a table. So
>> this is feedback from the 'typedef'
>> to the lexer.
>>
>
> You're referring to
>
> http://en.wikipedia.org/wiki/The_lexer_hack
>
>
>> So we at least need feedback to the lexer from the parse. I know we need
>> feedback from cpp
>> to the lexer. I will think of it.
>>
>
> No, CPP runs completely before anything else is done; there is no
> "feedback". This is also a debugging feature, e.g., you send a preprocessed
> source file when reporting a compiler bug so that the compiler devs don't
> have to reproduce your environment.
>

But it makes it impossible to go back to the source that produced it, which
someone we let compiler people
get away with. If you really want to understand what is happening, you have
to put the preprocessor info in
your AST.

   Matt

-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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