Re: iterator==0? (std::list::iterator)

From:

"Dani" <anonymous@discussions.microsoft.com>

Newsgroups:

microsoft.public.vc.stl

Date:

Wed, 15 Aug 2007 19:11:35 +0200

Message-ID:

<OlT0Pc13HHA.4184@TK2MSFTNGP06.phx.gbl>

I know how iterators work.
I just need one iterator to possibly represent an object from one list, or
another one, or to represent an invalid one... Not just one list... But all
of the lists are based on the same type.
But there's no 'invalid iterator', so like I said, I'm gonna use another
variable for this.

"Jeff Flinn" <Jeff@news.microsoft.com> wrote in message
news:uPJfpw03HHA.2064@TK2MSFTNGP03.phx.gbl...

Dani wrote:

"Ulrich Eckhardt" <eckhardt@satorlaser.com> wrote in message
news:plvap4-gpm.ln1@satorlaser.homedns.org...

Dani wrote:

If I set and iterator to 0

This doesn't work, and if it works the results are not guaranteed by the
C++
standard. This topic came up right here with the subject "assigning NULL
to
an iterator", please read the archives.

Uli

The thing is i'm using std::list so I can't just use an index
([]operator) and use -1 for invalid, So I guess I'm gonna define
a bool variable to determine if the iterator is
valid.

See examples for usage of std::find, which returns the end iterator:

...

std::list<int> ints;

...

if( ints.end() == std::find( ints.begin(), ints.end(), 123 ) )
{
// 123 not found
}

You need to educate yourself on the concepts behind iterators, containers
and ranges. These are built upon the concept of a half-open range. That
is, the end iterator is one past the end of the iterable items. This
indicates what you refer to above as an 'invalid' item position.

Jeff