[boost] Re: Formal Review: FOREACH macro

From: Arkadiy Vertleyb (vertleyb_at_[hidden])
Date: 2005-05-08 17:24:09

"Andrei Alexandrescu (See Website For Email)"  wrote

> Here's what I think. I am trying to encourage everyone - and yes, that
> includes myself - to think out of the box. It's very easy to say
> something cannot be done, or can only be done some cumbersome way. But
> usually, those answers come from straight within the box. And they come
> with the entire garnishment of irony, sarcasm, "proofs", what have you.
> But once we stop glorifying the box and decide to get out of it,
> solutions will be found - and they might even be better. :o)

Any solution that would

1) allow for non-trivial code generation based on the user input, and
2) would not require end users to download external tools,

would be fine with me.  Right now I can only see one such solution, but
maybe I am missing something.

And I am not saying that what we have now is perfect.  The biggest problem
with PP and Boost PP, IMO, is re-entrancy issues that are caused by the lack
of recursion in PP.  Just allowing recursion for function-like macros would
make our lifes a lot easier.  Limitations caused by the fact that inside
Boost PP the repetition is done manually, also dont make one too happy.

My whole point is, that _today_, despite all the problems, Boost PP proves
to be a very poverful tool allowing non-trivial code generation.  If
something like this existed 10 years ago, we would need neither MFC class
wizards nor IDL compiler.  Is it "cumbersome"?  I don't know -- is template
metaprogramming "cumbersome"?  I really believe they are very much alike.
Both were not in the initial design, both were later discovered, and both
are now "glorified" by some people, and hated by the others.  IMO, both are
not perfect (something seldom is perfect, if it's not in the initial
design), but OK -- they allow to achieve pretty interesting effect,
especially if used together.

Recall, that the discussion started with me trying to argue with the point
that "macros are bad because they are bad".  I am just saying that today
such a point is no longer axiomatic -- it needs to be proven.  The prove for
me would include providing a better alternative.

Regards,
Arkadiy