Re: [boost] [foreach] BOOST_AUTO_FOREACH

From: Eric Niebler (eric_at_[hidden])
Date: 2007-06-09 14:28:30

Matias Capeletto wrote:
> Hi all,
> 
> I want to combine BOOST_FOREACH and BOOST_AUTO in my code.
> With the current libs can do something like:
> 
> BOOST_FOREACH( BOOST_TYPEOF( *c.begin() ) v, c )
> {
>     ...
> }
> 
> I was wondering if this kind of use can be promote to a more
> user friendly syntax like:
> 
> BOOST_AUTO_FOREACH( v, c )
> {
>      ...
> }

Or ...

  #define BOOST_AUTO_FOREACH( x, y )\
     BOOST_FOREACH( BOOST_TYPEOF( *boost::begin(y) ) x, y )

There are some problems with this. There is no way to specify that you 
want to iterate by reference instead of by value. Also, if y has a 
dependent type, we'd need to use BOOST_TYPEOF_TPL instead, giving rise 
to the blasphemous BOOST_AUTO_FOREACH_TPL. Yuk. Finally, I do NOT want 
to create a dependency between foreach.hpp and typeof.hpp.

Considering the problems, I'm inclined to leave it out. You're certainly 
free to define your own.

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com