Class vec2

jni/venus/vec2.h:9–242

template <typename T>
class vec2
{
public:

// https://msdn.microsoft.com/en-us/library/2c8f766e.aspx
#ifdef _WIN32
#  pragma warning(push)
#  pragma warning(disable: 4201)  // warning C4201: nonstandard extension used: nameless struct/union
#endif
	union
	{
		T data[2];
		struct { T x, y; }; // 2D coordinate
		struct { T i, j; }; // index, integer pair
		struct { T s, t; }; // texture
		struct { T u, v; }; // texture
		
		struct { T gray, alpha;   }; // color
		struct { T rho, theta;    }; // polar coordinate
		struct { T width, height; }; // size
		struct { T column, row;   }; // grid, index, notice the order
		struct { T min, max;      }; // 1D AABB
		struct { T slice, stack;  }; // cut shape
	};

#ifdef _WIN32
#  pragma warning(pop)
#endif

	typedef T value_type;

public:
	vec2()  = default;
	~vec2() = default;

	explicit vec2(const T *array): x(array[0]), y(array[1]) { }
	explicit vec2(T scalar): x(scalar), y(scalar) { }
	vec2(T x, T y): x(x), y(y) { }

	vec2(const vec2<T>& v): x(v.x), y(v.y) {}

	vec2<T>& operator =(const vec2<T>& rhs)
	{
		if(this != &rhs)
		{
			x = rhs.x;
			y = rhs.y;
		}
		return *this;
	}

	// assignment operators
	vec2<T>& operator +=(const vec2<T>& rhs) { x += rhs.x; y += rhs.y; return *this; }
	vec2<T>& operator -=(const vec2<T>& rhs) { x -= rhs.x; y -= rhs.y; return *this; }
	vec2<T>& operator *=(T value)            { x *= value; y *= value; return *this; }
	vec2<T>& operator /=(T value)            { x /= value; y /= value; return *this; }

	/**