Thanks very much for all your replies. I wrote

However, for maps, the second variation (declaring outside the macro) doesn't work:

map m; ... FOREACH (map::value_type i, m) {...} // compiles map::value_type i; FOREACH (i, m) {...} // COMPILE ERROR

And the various replies are right on the money, and appreciated. I thought it was something like this, but I couldn't quite figure out what was going on. If anyone's interested: I'm playing with the idea of extending FOREACH in a way so that, instead of having a pair<>, you've got two separate variables for key and value. Maybe something like: map m; ... FOREACH_PAIR(int key, int value, m) { ... } I'm having a very moderate amount of success. Anyone else playing with this sort of thing? Thanks again! ---------------------------------------------------------------------- Dave Steffen, Ph.D. "The only justification for our concepts and Software Engineer IV systems of concepts is that they serve to Numerica Corporation represent the complex of our experiences; ph (970) 419-8343 x27 beyond this they have no legitimacy." fax (970) 223-6797 -- Albert Einstein dgsteffen@numerica.us

Eric Niebler writes:

Dave Steffen wrote:

...

If anyone's interested: I'm playing with the idea of extending FOREACH in a way so that, instead of having a pair<>, you've got two separate variables for key and value. Maybe something like:

map m; ... FOREACH_PAIR(int key, int value, m) { ... }

I'm having a very moderate amount of success. Anyone else playing with this sort of thing?

Can't find the reference now, but someone suggested using tie() from the tuples library for this:

int key, int value; BOOST_FOREACH(boost::tie(key, value), m) { ... }

Ah, yes, this is the sort of thing I was after. I'll look into it. Every loop I've written for the past two weeks has turned out to be an iteration over a map of some sort; they are, now, all FOREACH loops. Being the lazy sort of programmer I am, I'm now looking for ways to customize FOREACH to make iteration over maps easier. Thanks very much! ---------------------------------------------------------------------- Dave Steffen, Ph.D. "The only justification for our concepts and Software Engineer IV systems of concepts is that they serve to Numerica Corporation represent the complex of our experiences; ph (970) 419-8343 x27 beyond this they have no legitimacy." fax (970) 223-6797 -- Albert Einstein dgsteffen@numerica.us

Martin wrote:

...

map m; ... FOREACH (map::value_type i, m) {...} // compiles map::value_type i; FOREACH (i, m) {...} // COMPILE ERROR

Why not

map::value_type& i; FOREACH (i, m) {...}

Would it not have to be FOREACH(map::value_type& i, m) { } ? Cheers Russell