Edit Question - KnowledgeHub

Title Body

What if I increment an iterator by 2 when it points onto the last element of a vector? In this question asking how to adjust the iterator to an STL container by 2 elements two different approaches are offered: either use a form of arithmetic operator - +=2 or ++ twice or use std::advance() I've tested both of them with VC++ 7 for the edge case when the iterator points onto the last element of the STL container or beyond: vector<int> vec; vec.push_back( 1 ); vec.push_back( 2 ); vector<int>::iterator it = vec.begin(); advance( it, 2 ); bool isAtEnd = it == vec.end(); // true it++; // or advance( it, 1 ); - doesn't matter isAtEnd = it == vec.end(); //false it = vec.begin(); advance( it, 3 ); isAtEnd = it == vec.end(); // false I've seen may times an advise to compare against vector::end() when traversing the vector and other containers: for( vector<int>::iterator it = vec.begin(); it != vec.end(); it++ ) { //manipulate the element through the iterator here } Obviously if the iterator is advanced past the last element inside the loop the comparison in the for-loop statement will evaluate to false and the loop will happily continue into undefined behaviour. Do I get it right that if I ever use advance() or any kind of increment operation on an iterator and make it point past the container's end I will be unable to detect this situation? If so, what is the best practice - not to use such advancements?

Tags (comma-separated) Cancel