A convenient iterator that prints a progress bar to the terminal.

progress.h

#ifndef PROGRESS_H
#define PROGRESS_H

#include <iostream>

template <class T>
class Progress {
public:

    class ProgressIterator {
    public:

        Progress<T> _owner;
        T _current;

        ProgressIterator(T current, Progress& owner)
          : _current(current),
            _owner(owner)
        {
        }

        void operator++()
        {
            _current += _owner._step;

            if (_current + _owner._step >= _owner._end) {
                _current = _owner._end;
            }

            int percent = static_cast<int>(100 * (_current - _owner._start) / (_owner._end - _owner._start));

            std::string bar;

            for(int i = 0; i < 50; i++){
                if (i < (percent / 2)) {
                    bar.replace(i, 1, "=");
                } else if( i == (percent / 2)){
                    bar.replace(i, 1, ">");
                } else{
                    bar.replace(i, 1, " ");
                }
            }

            // Hide cursor
            std::cout << "\e[?25l";

            std::cout << "\r" "[" << bar << "] ";
            std::cout.width(3);
            std::cout << percent << "%     " << std::flush;

            if (_current == _owner._end) {
                std::cout << std::endl;
                // Show cursor
                std::cout << "\e[?25h";
            }

        }

        bool operator!=(const ProgressIterator& other) const {
            return !(_current == other._current);
        }

        T operator*() {
            return _current;
        }

    };

    Progress(T start, T end, T step)
      : _start(start),
        _end(end),
        _step(step)
    {
    }

    Progress(T start, T end)
      : _start(start),
        _end(end),
        _step(1)
    {
    }

    ProgressIterator begin() {
        return Progress<T>::ProgressIterator(_start, *this);
    }

    ProgressIterator end() {
        return Progress<T>::ProgressIterator(_end, *this);
    }

private:

    T _start;
    T _end;
    T _step;
};

#endif /* end of include guard: PROGRESS_H */