// Basic ranges in C++ #include #include template class range { private: // Customized forward iterator // http://www.cplusplus.com/reference/iterator/ForwardIterator/ struct __iterator { using iterator_category = std::forward_iterator_tag; using value_type = _T; using difference_type = std::ptrdiff_t; using pointer = _T*; using reference = _T&; constexpr __iterator( _T v, _T increment ) : m_Increment( increment ), m_Value( v ){} constexpr _T operator*() const { return m_Value; } constexpr bool operator!=( const __iterator& other ) const { return m_Increment < 0 ? m_Value > other.m_Value : m_Value < other.m_Value; } constexpr operator _T() const { return m_Value; } constexpr __iterator& operator++(){ m_Value += m_Increment; return *this; } private: const _T m_Increment; _T m_Value; }; public: constexpr range( _T max ); constexpr range( _T min, _T max ); constexpr range( _T min, _T max, _T increment ); constexpr __iterator begin() const { return m_Ptr; } constexpr __iterator end() const { return m_End; } constexpr __iterator cbegin() const { return m_Ptr; } constexpr __iterator cend() const { return m_End; } private: __iterator m_Ptr; __iterator m_End; // Max ( exclusive ) }; template constexpr range<_T>::range( _T max ) : range( 0, max, 1 ) {} template constexpr range<_T>::range( _T min, _T max ) : range( min, max, 1 ) {} template constexpr range<_T>::range( _T min, _T max, _T increment ) : m_Ptr( min, increment ) , m_End( max, increment ) {} #include #include int main() { std::cout << "range( 5 ):\n"; for( auto i : range( 5 ) ) { std::cout << i << '\n'; } std::cout << "\nrange( 3, 8 ):\n"; for( auto i : range( 3, 8 ) ) { std::cout << i << '\n'; } std::cout << "\nrange( 0, 50, 5 ):\n"; for( auto i : range( 0, 50, 5 ) ) { std::cout << i << '\n'; } // Can also fill a vector with it, instead of just printing them constexpr auto R = range( 0, 50, 5 ); std::vector v( R.begin(), R.end() ); }

C++ Ranges