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

A certain type of rounding is also implemented in Boost:

#include 

#include 

template T round2(const S& x) {
  typedef boost::numeric::conversion_traits Traits;
  typedef boost::numeric::def_overflow_handler OverflowHandler;
  typedef boost::numeric::RoundEven Rounder;
  typedef boost::numeric::converter Converter;
  return Converter::convert(x);
}

int main() {
  std::cout << round2(0.1) << ' ' << round2(-0.1) << ' ' << round2(-0.9) << std::endl;
}

Note that this works only if you do a to-integer conversion.