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

Subject: Re: [Boost-users] [foreach] BOOST_FOREACH question...
From: Dmitry Vinogradov (sraider_at_[hidden])
Date: 2010-01-07 20:14:38

> Does the BOOST_FOREACH macro work for empty sequences or must a size check
> be done explicitly?
>
>
>          list<int>  mylist;
>
>          if (!mylist.empty())    //<--- necessary?
>          {
>              foreach(int&  i, mylist)
>              {
>                  // take action
>              }
>          }
>
>
> The reason I ask is that neither begin() nor end() return valid iterators
> for empty sequences, but it is my understanding that BOOST_FOREACH needs
> iterators to work properly.

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.