Re: Query regarding iterators and vector

From:
"Daniel T." <daniel_t@earthlink.net>
Newsgroups:
comp.lang.c++
Date:
Sat, 05 Jul 2008 10:10:43 -0400
Message-ID:
<daniel_t-C8B00E.10104205072008@earthlink.vsrv-sjc.supernews.net>
Jerry Coffin <jcoffin@taeus.com> wrote:

prasadmpatil@gmail.com says...

I am new STL programming.
I have a query regarding vectors. If I am iterating over a vector
using a iterator, but do some operations that modify the size of the
vector. Will the iterator recognize this?

I wrote the following program to test this out.

#include <fstream>
#include <iostream>
#include <string>
#include <vector>

using namespace std;

int main()
{
    vector<int> a;

    a.push_back(1);
    a.push_back(2);
    a.push_back(3);
    cout<<"Vector test begin"<<endl;
    vector<int>::iterator iter0;
    for(iter0=a.begin(); iter0!=a.end(); iter0++)
    {
        cout << "\n value: " << (*iter0)<<endl;
        if(*iter0 == 2)
        {
            a.push_back(4);
            a.push_back(5);
        }
    }
    cout<<"Vector test end";
}


A push_back on a vector invalidates all iterators into that vector.


Not quite true. push_back only invalidates the iterators if size() <
capacity() before the push_back occurs. If the OP had done a reserve(5)
before entering the loop, all would have been well.

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