Apologies for the non-text formatting. Here is the same message in pure text: Hello, boost/trunk/libs/math/doc/sf_and_dist/html/math_toolkit/utils/rounding/round.html says that: Halfway cases are rounded away from zero, regardless of the current rounding direction. This I believe is compatible with C99 TC3 and therefore the latest C++1x draft. However, when I ran this program: #include <cmath> #include <iostream> #include inline double round1(double x) { if (x >= 0.0) return std::floor(x + 0.5); else return std::ceil(x - 0.5); } inline double round2(double x) { return std::floor(x + 0.5); } int main() { std::cout.setf(std::ios_base::fixed, std::ios_base::floatfield); std::cout.precision(1); std::cout<< "d floor/ceil.5 floor.5 boostmathround"<