line_iter.hpp

#pragma once
 
#include <istream>
#include <iterator>
#include <string>
 
namespace dl::utils {
    struct LineIterator final {
        using iterator_category = std::input_iterator_tag;
        using value_type = std::string;
        using difference_type = std::ptrdiff_t;
        using reference = const value_type&;
        using pointer = const value_type*;
 
        LineIterator() : input_(nullptr) {}
        LineIterator(std::istream& input) : input_(&input) { ++*this; }
 
        reference operator*() const { return s_; }
        pointer operator->() const { return &**this; }
 
        LineIterator& operator++() {
            if (!std::getline(*input_, s_))
                input_ = nullptr;
            return *this;
        }
 
        LineIterator operator++(int) {
            auto copy(*this);
            ++*this;
            return copy;
        }
 
        friend bool operator==(const LineIterator& x, const LineIterator& y) { return x.input_ == y.input_; }
 
        friend bool operator!=(const LineIterator& x, const LineIterator& y) { return !(x == y); }
 
    private:
        std::istream* input_;
        std::string s_;
    };
} // namespace dl::utils