Class vec4

jni/venus/vec4.h:14–158

 */
template <typename T>
class vec4
{
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[4];
		struct {T x, y, z, w;}; // 4D homogeneous coordinate
		struct {T r, g, b, a;}; // color
		struct {T s, t, p, q;}; // texture
	};

#ifdef _WIN32
#  pragma warning(pop)
#endif

	typedef T value_type;

public:
	vec4()  = default;
	~vec4() = default;

	explicit vec4(const T *array): x(array[0]), y(array[1]), z(array[2]), w(array[3]) { }
	explicit vec4(T scalar): x(scalar), y(scalar), z(scalar), w(scalar) { }
	vec4(T x, T y, T z, T w): x(x), y(y), z(z), w(w) { }

	vec4(const vec4<T>& v): x(v.x), y(v.y), z(v.z), w(v.w) { }
	vec4<T>& operator =(const vec4<T>& rhs)
	{
		if(this != &rhs)
		{
			x = rhs.x;
			y = rhs.y;
			z = rhs.z;
			w = rhs.w;
		}
		return *this;
	}

	T& operator[] (std::size_t i) { return _data[i]; }
	const T& operator[] (std::size_t i) const { return _data[i]; }

	// assignment operators
	vec4<T>& operator +=(const vec4<T>& rhs) { x += rhs.x; y += rhs.y; z += rhs.z; w += rhs.w; return *this; }
	vec4<T>& operator -=(const vec4<T>& rhs) { x -= rhs.x; y -= rhs.y; z -= rhs.z; w -= rhs.w; return *this; }
	vec4<T>& operator *=(T value)            { x *= value; y *= value; z *= value; w *= value; return *this; }
	vec4<T>& operator /=(T value)            { x /= value; y /= value; z /= value; w /= value; return *this; }

	// unary operators
	vec4<T> operator +() const { return vec4<T>(+x, +y, +z, +w); }
	vec4<T> operator -() const { return vec4<T>(-x, -y, -z, -w); }

	// binary operators, multiply and divide operations for scalar