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

It may be worth noting that if you wanted an integer result from the rounding you don't need to pass it through either ceil or floor. I.e.,

int round_int( double r ) {
    return (r > 0.0) ? (r + 0.5) : (r - 0.5); 
}