Can you explain what a forward_iterator type iterator in C++ is?

A forward iterator in C++ is a type of iterator that supports traversing a sequence of elements in one direction (forward). It allows:

• reading (and sometimes modifying) elements as you progress;
• using increment operators (++it or it++);
• comparing iterators for equality or inequality.

Unlike an input iterator, a forward iterator guarantees that you can traverse the same element multiple times (multi-pass iterator). However, it does not support moving backwards like a bidirectional iterator, nor does it allow arbitrary access like a random access iterator.

Example of using a forward iterator:

#include <forward_list>
#include <iostream>

int main() {
    std::forward_list<int> fl = {1, 2, 3, 4};
    for (auto it = fl.begin(); it != fl.end(); ++it) {
        std::cout << *it << " ";
    }
    return 0;
}

Here, the iterator allows traversal of the list only forward.