std::nearbyint,std::nearbyintf,std::nearbyintl (3) - Linux Man Pages
Defined in header <cmath>
float nearbyint ( float arg ); (1) (since C++11)
float nearbyintf( float arg );
double nearbyint ( double arg ); (2) (since C++11)
long double nearbyint ( long double arg ); (3) (since C++11)
long double nearbyintl( long double arg );
double nearbyint ( IntegralType arg ); (4) (since C++11)
1-3) Rounds the floating-point argument arg to an integer value in floating-point format, using the current_rounding_mode.
4) A set of overloads or a function template accepting an argument of any integral_type. Equivalent to (2) (the argument is cast to double).
arg - floating point value
The nearest integer value to arg, according to the current_rounding_mode, is returned.
This function is not subject to any of the errors specified in math_errhandling.
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
* FE_INEXACT is never raised
* If arg is ±∞, it is returned, unmodified
* If arg is ±0, it is returned, unmodified
* If arg is NaN, NaN is returned
The only difference between std::nearbyint and std::rint is that std::nearbyint never raises FE_INEXACT.
The largest representable floating-point values are exact integers in all standard floating-point formats, so std::nearbyint never overflows on its own; however the result may overflow any integer type (including std::intmax_t), when stored in an integer variable.
If the current rounding mode is FE_TONEAREST, this function rounds to even in halfway cases (like rint, but unlike round).
// Run this code
llrintf nearest integer using current rounding mode with
llrintl exception if the result differs