Re: [Boost-users] [foreach] BOOST_FOREACH question...

On 1/8/2010 1:40 PM, barcaroller wrote:

"Dmitry Vinogradov" wrote:

...

To be short: it's not necessary.

BTW, begin() and end() for an empty list are valid. You can't dereference them, but they are valid. So one can use them for comparison. And BOOST_FOREACH does.

I've had problems with standard 'for' loops when using empty containers:

for (i = mylist.begin() ; i != mylist.end() ; i++)

That's perfectly OK.

By problems I mean core-dumps, memory leaks, etc. These problems went away when I used a size check:

if (!mylist.empty()) for (i = mylist.begin() ; i != mylist.end() ; i++)

This leads me to believe that begin() and end() are not valid, or is there another way to explain this?

I suggest you look for the problem elsewhere. list::begin and list::end always return valid iterators. Comparing them is fine -- if the list is empty, the begin and end iterators will compare equal. -- Eric Niebler BoostPro Computing http://www.boostpro.com