浮点数的二分

while(r-l<eps)//其中eps是所需要的精度
{
    mid = (l+r)/2;
    ...
}

const double eps = 1e-5;
double f(double x)
{
    return x * x; //函数f(x)=x^2
}

double calSqrt()
{
    double left = 1, right = 2;
    double mid;
    while (right - left > eps) //当条件不满足精度条件时退出
    {
        mid = (right + left) / 2; //取left和right的中点
        if (f(mid) > 2)  //如果f(mid)在
            right = mid;
        else
            left = mid;
    }
    return mid;
}

const double eps = 1e-5;
double f(double x)
{
    return x * x - 2;
}

double calSqrt()
{
    ......
    while (right - left > eps)
    {
        ......
        if (f(mid) > 0)
        ......
    }
    return mid;
}

const double eps = 1e-5;
double f(double x)
{
    return ....;
}

double solve(double L, double R)
{
    double left = L, right = R; //[left,right]=[L,R]
    double mid;
    while (right - left > eps)
    {
        mid = (right + left) / 2;
        if (f(mid) > 0)
            right = mid;
        else
            left = mid;
    }
    return mid;
}