std::nearbyint, std::nearbyintf, std::nearbyintl
Defined in header <cmath> | ||
| (1) | ||
float nearbyint (float num ); double nearbyint (double num ); | (until C++23) | |
/*floating-point-type*/ nearbyint (/*floating-point-type*/ num ); | (since C++23) | |
float nearbyintf(float num ); | (2) | (since C++11) |
longdouble nearbyintl(longdouble num ); | (3) | (since C++11) |
SIMD overload(since C++26) | ||
Defined in header <simd> | ||
template</*math-floating-point*/ V > constexpr/*deduced-simd-t*/<V> | (S) | (since C++26) |
Additional overloads(since C++11) | ||
Defined in header <cmath> | ||
template<class Integer > double nearbyint ( Integer num ); | (A) | |
std::nearbyint for all cv-unqualified floating-point types as the type of the parameter.(since C++23)S) The SIMD overload performs an element-wise std::nearbyint on v_num.
| (since C++26) |
A) Additional overloads are provided for all integer types, which are treated as double. | (since C++11) |
Contents |
[edit]Parameters
| num | - | floating-point or integer value |
[edit]Return value
The nearest integer value to num, according to the current rounding mode, is returned.
[edit]Error handling
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 num is ±∞, it is returned, unmodified.
- If num is ±0, it is returned, unmodified.
- If num is NaN, NaN is returned.
[edit]Notes
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 std::rint, but unlike std::round).
The additional overloads are not required to be provided exactly as (A). They only need to be sufficient to ensure that for their argument num of integer type, std::nearbyint(num) has the same effect as std::nearbyint(static_cast<double>(num)).
[edit]Example
#include <cfenv>#include <cmath>#include <iostream>#pragma STDC FENV_ACCESS ON int main(){std::fesetround(FE_TONEAREST);std::cout<<"rounding to nearest: \n"<<"nearbyint(+2.3) = "<< std::nearbyint(2.3)<<" nearbyint(+2.5) = "<< std::nearbyint(2.5)<<" nearbyint(+3.5) = "<< std::nearbyint(3.5)<<'\n'<<"nearbyint(-2.3) = "<< std::nearbyint(-2.3)<<" nearbyint(-2.5) = "<< std::nearbyint(-2.5)<<" nearbyint(-3.5) = "<< std::nearbyint(-3.5)<<'\n'; std::fesetround(FE_DOWNWARD);std::cout<<"rounding down:\n"<<"nearbyint(+2.3) = "<< std::nearbyint(2.3)<<" nearbyint(+2.5) = "<< std::nearbyint(2.5)<<" nearbyint(+3.5) = "<< std::nearbyint(3.5)<<'\n'<<"nearbyint(-2.3) = "<< std::nearbyint(-2.3)<<" nearbyint(-2.5) = "<< std::nearbyint(-2.5)<<" nearbyint(-3.5) = "<< std::nearbyint(-3.5)<<'\n'; std::cout<<"nearbyint(-0.0) = "<< std::nearbyint(-0.0)<<'\n'<<"nearbyint(-Inf) = "<< std::nearbyint(-INFINITY)<<'\n';}
Output:
rounding to nearest: nearbyint(+2.3) = 2 nearbyint(+2.5) = 2 nearbyint(+3.5) = 4 nearbyint(-2.3) = -2 nearbyint(-2.5) = -2 nearbyint(-3.5) = -4 rounding down: nearbyint(+2.3) = 2 nearbyint(+2.5) = 2 nearbyint(+3.5) = 3 nearbyint(-2.3) = -3 nearbyint(-2.5) = -3 nearbyint(-3.5) = -4 nearbyint(-0.0) = -0 nearbyint(-Inf) = -inf
[edit]See also
(C++11)(C++11)(C++11)(C++11)(C++11)(C++11)(C++11)(C++11)(C++11) | nearest integer using current rounding mode with exception if the result differs (function) |
(C++11)(C++11)(C++11)(C++11)(C++11)(C++11)(C++11)(C++11)(C++11) | nearest integer, rounding away from zero in halfway cases (function) |
(C++11)(C++11) | gets or sets rounding direction (function) |
C documentation for nearbyint | |
