Roddy Roddy - 3 months ago 16
C++ Question

round() for float in C++

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 ceil() and floor() in the math.h - but not round().

Is it present in the standard C++ library under another name, or is it missing??

Answer

There's no round() in the C++98 standard library. You can write one yourself though:

double round(double d)
{
  return floor(d + 0.5);
}

The probable reason there is no round function in the C++98 standard library is that it can in fact be implemented in different ways. The above is one common way but there are others such as round-to-even, which is less biased and generally better if you're going to do a lot of rounding; it's a bit more complex to implement though.

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