iota iterator

gistfile1.cpp

template <typename T>
struct iota_iterator : std::iterator<std::random_access_iterator_tag, T> {
    typedef std::iterator<std::random_access_iterator_tag, T> base_t;
    typedef typename base_t::difference_type difference_type;

    iota_iterator(T value = T()) : value(value) { }

    iota_iterator& operator ++() {
        ++value;
        return *this;
    }

    iota_iterator operator ++(int) {
        iota_iterator copy = *this;
        ++*this;
        return copy;
    }

    iota_iterator& operator --() {
        --value;
        return *this;
    }

    iota_iterator operator --(int) {
        iota_iterator copy = *this;
        --*this;
        return copy;
    }

    iota_iterator& operator +=(difference_type n) {
        value += n;
        return *this;
    }

    iota_iterator operator +(difference_type n) {
        return iota_iterator(value + n);
    }

    friend iota_iterator operator +(difference_type n, iota_iterator const& i) {
        return i + n;
    }

    iota_iterator& operator -=(difference_type n) {
        value -= n;
        return *this;
    }

    iota_iterator operator -(difference_type n) {
        return iota_iterator(value - n);
    }

    difference_type operator -(iota_iterator other) {
        return value - other.value;
    }

    T operator [](difference_type n) const {
        return value + n;
    }

    // Not available -- we implement a const_iterator concept.
    //T& operator [](difference_type n);

    T const& operator *() const {
        return value;
    }

    T const* operator ->() const {
        return &value;
    }

    friend bool operator ==(iota_iterator const& lhs, iota_iterator const& rhs) {
        return lhs.value == rhs.value;
    }

    friend bool operator !=(iota_iterator const& lhs, iota_iterator const& rhs) {
        return not (lhs == rhs);
    }

private:
    T value;
};