[boost] Re: Formal Review: FOREACH macro

From: David Abrahams (dave_at_[hidden])
Date: 2005-05-09 08:19:56

"Andrei Alexandrescu (See Website For Email)" <SeeWebsiteForEmail_at_[hidden]> writes:

> This is, unsurprisingly, a major effort, and boost would be a
> crucible of the size and expertise needed to pull it off.

I think solving the "syntactic metaprogramming problem" really
requires familiarity with and access to the source code of a C++
compiler.  I don't think we have much of that around here, despite the
existence of g++.

> The way I see things, there are three ways:
>
> 1. Start from the Boost implementation of the C++ preprocessor, and
> add sane features to it. Keep the old preprocessor features as
> deprecated.

That one's a possibility.  I personally would not want to solve these
problems in the preprocessor layer because I want better integration
with the rest of the language than that approach can offer.  Others
may feel differently, of course.

> 2. Agree on a standard text preprocessing tool (perl, awk, sed, m4...) 
> and write some utilities tailored for C++ tasks.

I've gone down this path, with unsatisfactory results.  Not interested
in this one.

> 3. Start an effort to add ways of manipulating ASTs to the native 
> language so as to eliminate the need for preprocessing.

That approach has promise.  Bjarne has a project to standardize a C++
program representation and manipulation library -- it could be
interesting to build a metaprogramming system around that.

> Given, however, the lack of traction that I sense around here, I
> think this group will be flooded with arguments on why all of 1, 2,
> and 3 are disadvantageous. 

Wow, I guess nobody would want to argue with you on any points for
fear of being part of the flood and confirming your "lack of
traction."  I think until this post of mine showed up, this last
sentence had the effect of quashing any further discussion of your
three ideas.  Instead we have a mostly-irrelevant thread about whether
TMP and PPMP are similar.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com