RE: [boost] Re: Formal Review: FOREACH macro

From: Paul Mensonides (pmenso57_at_[hidden])
Date: 2005-05-08 22:35:21

> -----Original Message-----
> From: boost-bounces_at_[hidden] 
> [mailto:boost-bounces_at_[hidden]] On Behalf Of Andrei 
> Alexandrescu (See Website For Email)

> Second, I disagree that the template engine and the 
> preprocessor are similar. I see very very little similarity. 
> The former is a mean pure functional language fostering 
> pattern matching, recursion, and sporting knowledge and high 
> integration with the non-templated part of C++.

What high integration are you referring to here?  I don't see much of a high
integration between template metaprogramming and the rest of the language.  In
fact, there is very little integration.  Instead, it's more like they coexist
without interferring with each other, and communication is entirely one way.
Even with the type system, the pattern-matching capabilities are limited to (in
essence) syntactic matching rather than more general property matching.  You
have to bend over backwards to do that (read: SFINAE).

So, again, what high integration are you referring to?  What I see instead is a
lot tricky techniques and a whole slew of specialized idioms to workaround the
basic lack of real integration.  Don't get me wrong, I'm not condemning template
metaprogramming or even specialized idioms and techniques.  Rather, the
development of those idioms and techniques are laudable examples of people
"thinking outside the box" to get something done given the tools that they have.
The same applies to preprocessor metaprogramming.

> The 
> computational model is known and powerful. In contrast, 
> programming based on the token-oriented preprocessor uses 
> arcane idioms and computations, which IMO just takes us back 
> 40 years.

What idioms are those?  This, BTW, from the perspective of a user, not library
internals.  What is really the difference, idiomwise, between fold(list, state),
fold<list, state>, and FOLD(list, state)?

Regards,
Paul Mensonides