Defined in header <cmath> | ||
---|---|---|
(1) | ||
float nearbyint ( float num ); double nearbyint ( double num ); long double nearbyint ( long double num ); | (until C++23) | |
/* floating-point-type */ nearbyint ( /* floating-point-type */ num ); | (since C++23) | |
float nearbyintf( float num ); | (2) | (since C++11) |
long double nearbyintl( long double num ); | (3) | (since C++11) |
Additional overloads (since C++11) | ||
Defined in header <cmath> | ||
template< class Integer > double nearbyint ( Integer num ); | (A) |
num
to an integer value in floating-point format, using the current rounding mode. The library provides overloads of std::nearbyint
for all cv-unqualified floating-point types as the type of the parameter. (since C++23)
double | (since C++11) |
num | - | floating-point or integer value |
The nearest integer value to num
, 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 num
is ±∞, it is returned, unmodified num
is ±0, it is returned, unmodified num
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 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))
.
#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
(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 |
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