From: Eric Niebler (eric_at_[hidden])
Date: 2004-05-07 22:33:21
David Abrahams wrote:
> Maybe
> something could be done with "goto"? I haven't looked at
> BOOST_FOREACH carefully, but I'm imagining something like:
>
> for (C::iterator s = c.begin(), f = c.end(); s != f; ++s) // outer
> {
> for(C::reference r = *s;;) // inner
> {
> // Body goes here
> goto continue_;
> }
> break; // if there's a break in the body, break out all the way
> continue_:
> }
That won't work. Look how BOOST_FOREACH is used:
BOOST_FOREACH( int &i, int_vector )
{
// body goes here
}
BOOST_FOREACH must expand to something such that the following scope is
treated as the loop body. There is no place to put the continue_ label,
and no place to put the goto. I thought about putting a goto somewhere
in the inner for loop, like "for( ...; ; goto continue_ )" but C++
doesn't allow that. And even if that worked, it's still borken because a
break in the loop body would skip the goto.
-- Eric Niebler Boost Consulting www.boost-consulting.com