C++11—迭代器类实现

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//迭代器类namespace detail_range{template <typename T>class iterator{public:using value_type = T;using size_type = size_t;private:size_type cursor_;const value_type step_;value_type value_;public:iterator(size_type cur_start, value_type begin_val, value_type step_val):cursor_(cur_start), step_(step_val), value_(begin_val){value_ += (step_*cursor_);}value_type operator*()const{return value_;}bool operator!=(const iterator&rhs)const{return (cursor_ != rhs.cursor_);}iterator& operator++(void){value_ += step_;++cursor_;return (*this);}};template<typename T>class impl{public:using value_type = T;using reference = const value_type&;using const_reference = const value_type&;using iterator = const detail_range::iterator<value_type>;using const_iterator = const detail_range::iterator<value_type>;using size_type = typename iterator::size_type;private:const value_type begin_;const value_type end_;const value_type step_;const size_type max_count_;size_type get_adjusted_count(void) const{if (step_ > 0 && begin_ >= end_){throw std::logic_error("End value must be greater than begin value.");}else if (step_<0 && begin_<end_){throw std::logic_error("End value must be less than begin value.");}size_type x = static_cast<size_type>((end_ - begin_) / step_);if (begin_ + (step_*x) != end_){++x;}return x;}public:impl(value_type begin_value, value_type end_val, value_type step_val):begin_(begin_value), end_(end_val), step_(step_val), max_count_(get_adjusted_count()){}size_type size(void) const{return max_count_;}const_iterator begin(void) const{return{ 0, begin_, step_ };}const_iterator end(void) const{return{ max_count_, begin_, step_ };}};template <typename T>detail_range::impl<T> range(T end){return{ {}, end, 1 };}template<typename T>detail_range::impl<T> range(T begin, T end){return{ begin, end, 1 };}template <typename T, typename U>auto range(T begin, T end, U step)->detail_range::impl<decltype(T + U)>{using r_t = detail_range::impl<decltype(begin + end)>;return r_t(begin, end, step);}void test_range(void){std::cout << "range(15): ";for (int i : range(15)){std::cout << "  " << i;}std::cout << std::endl;}}//namespace detail_rangeint main(){detail_range::test_range();return 0;}
其中test_range为测试函数
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