求助：c++求pi,编译通过，但运行后无任何结果？

Question

#include "stdafx.h"
#include
using namespace std;

int main()
{
double arctan(double);
cout << "pi= " << 16 * arctan(1 / 5.0) - 4 * arctan(1 / 239.0) << endl;
return 0;
}

double arctan(double x)
{
double result = 0;
int i = 1, k = 1;
do
{
for (k = 1; k <= (2 * i - 1); k++)
k *= x;
switch (i % 2)
{
case 1:
result += (k / (2 * i - 1)); break;
case 0:
result -= (k / (2 * i - 1)); break;
}
i++;
} while (k > 1e-15);
return result;
}

Answer 1

 #include<iostream>
using namespace std;

double arctan(double);

int main()
{
    cout << "pi= " << 16 * arctan(1 / 5.0) - 4 * arctan(1 / 239.0) << endl;
    return 0;
}

double arctan(double x)
{
    double result = 0;
    int i = 1, s = 1;
        double k = 1.0;
    do
    {
        double t = 1;
        for (int j = 0; j < (i * 2 - 1); j++)
            t *= x;
                k = t / (double)(i * 2 - 1) * (double)s;
        result = result + k;
        s = -s;
        i++;
    } while (k > 1e-15);
    return result;
}