constexpr.cpp

int x = 2;

constexpr int GetDays() { return 2018 * 365; }

constexpr int todayDays1 = GetDays() * 1; // OK
constexpr int todayDays2 = GetDays() * x; // CompileTime Error

const int todayDays = GetDays() * x; // OK, Runtime initialize


class CVector2
{
private:
	float m_x;
	float m_y;

	constexpr static float square(float x) { return x * x; }

public:
	constexpr CVector2(float x, float y)
		: m_x(x), m_y(y)
	{}

	constexpr float GetLengthSquare() const
	{
		return square(m_x) + square(m_y);
	}
};

void ConstExprTest()
{
	constexpr CVector2 vec2(5.0f, 6.0f);

	// asm lea, call, fstp (런타임 처리)
	const float vec2LengthSquare1 = vec2.GetLengthSquare();

	// asm 2 moves (컴파일타임에 계산된 것 이용)
	constexpr float vec2LengthSquare2 = vec2.GetLengthSquare();
}