round() for float in C++

Question

I need a simple floating point rounding function, thus:

double round(double);

round(0.1) = 0
round(-0.1) = 0
round(-0.9) = -1

I can find

Answer 1

Function double round(double) with the use of the modf function:

double round(double x)
{
    using namespace std;

    if ((numeric_limits::max() - 0.5) <= x)
        return numeric_limits::max();

    if ((-1*std::numeric_limits::max() + 0.5) > x)
        return (-1*std::numeric_limits::max());

    double intpart;
    double fractpart = modf(x, &intpart);

    if (fractpart >= 0.5)
        return (intpart + 1);
    else if (fractpart >= -0.5)
        return intpart;
    else
        return (intpart - 1);
    }

To be compile clean, includes "math.h" and "limits" are necessary. The function works according to a following rounding schema:

• round of 5.0 is 5.0
• round of 3.8 is 4.0
• round of 2.3 is 2.0
• round of 1.5 is 2.0
• round of 0.501 is 1.0
• round of 0.5 is 1.0
• round of 0.499 is 0.0
• round of 0.01 is 0.0
• round of 0.0 is 0.0
• round of -0.01 is -0.0
• round of -0.499 is -0.0
• round of -0.5 is -0.0
• round of -0.501 is -1.0
• round of -1.5 is -1.0
• round of -2.3 is -2.0
• round of -3.8 is -4.0
• round of -5.0 is -5.0