C++模板元编程编译期计算实例

template <int N>
struct Factorial {
    static constexpr int value = N * Factorial<N - 1>::value;
};
template <>
struct Factorial<0> {
static constexpr int value = 1;
};

constexpr int result = Factorial<5>::value; // 结果为 120

template <int N>
struct Fibonacci {
    static constexpr int value = Fibonacci<N-1>::value + Fibonacci<N-2>::value;
};
template <>
struct Fibonacci<0> {
static constexpr int value = 0;
};
template <>
struct Fibonacci<1> {
static constexpr int value = 1;
};

constexpr int fib5 = Fibonacci<5>::value; // 结果为 5

constexpr int factorial(int n) {
    return (n <= 1) ? 1 : n * factorial(n - 1);
}

constexpr int val = factorial(5); // 编译期计算为 120