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× C++ Standard Library C++ STL Library


The FE_TONEAREST macro expands to a value of type int, which can be used with fesetround and fegetround functions to indicate to-nearest rounding direction. Rounding x to-nearest gives the possible value that is nearest to x. For halfway cases, it is rounded away from zero.

Definition in the <cfenv> header file is:

#define FE_TONEAREST  /*implementation defined*/                

All possible rounding direction modes are given below:

MacrosDescription
FE_DOWNWARD Rounding towards negative infinity.
FE_TONEAREST Rounding towards nearest representable value.
FE_TOWARDZERO Rounding towards zero.
FE_UPWARD Rounding towards positive infinity.

Certain library implementations may define additional floating-point rounding direction macro constants (with their corresponding macros also beginning with FE_).

Example:

The below example shows the usage of FE_TONEAREST macro.

#include <iostream>
#include <cfenv>
#include <cmath>

#pragma STDC FENV_ACCESS ON

using namespace std;
 
int main (){
  //to-nearest rounding direction mode
  fesetround(FE_TONEAREST);

  cout<<"rint(10.2) = "<<rint(10.2)<<"\n";
  cout<<"rint(10.8) = "<<rint(10.8)<<"\n";
  cout<<"rint(-5.2) = "<<rint(-5.2)<<"\n";
  cout<<"rint(-5.8) = "<<rint(-5.8)<<"\n";

  return 0;
}

The output of the above code will be:

rint(10.2) = 10
rint(10.8) = 11
rint(-5.2) = -5
rint(-5.8) = -6

❮ C++ <cfenv> Library