如何在C++中使用不同的数字？

int a = 10;
float b = 3.14;
double c = 1.23456789;
long d = 123456789;

#include <cmath>

int main() {
    double x = 2.0;
    double y = 3.0;
    double z = pow(x, y); // z = x^y = 2^3 = 8
    double w = sqrt(x); // w = sqrt(2)
    return 0;
}

#include<vector>

int main() {
    std::vector<int> int_vector = {1, 2, 3, 4, 5};
    std::vector<float> float_vector = {1.1, 2.2, 3.3, 4.4, 5.5};
    return 0;
}

template<typename T>
T add(T a, T b) {
    return a + b;
}

int main() {
    int x = 10;
    int y = 20;
    int z = add<int>(x, y); // z = 30

    double p = 3.14;
    double q = 2.71;
    double r = add<double>(p, q); // r = 5.85

    return 0;
}