std::exp2, std::exp2f, std::exp2l
From cppreference.com
C++
Feature test macros (C++20)
Concepts library (C++20)
Metaprogramming library (C++11)
Ranges library (C++20)
Filesystem library (C++17)
Concurrency support library (C++11)
Execution control library (C++26)
Numerics library
Mathematical special functions (C++17)
Mathematical constants (C++20)
Basic linear algebra algorithms (C++26)
Data-parallel types (SIMD) (C++26)
Floating-point environment (C++11)
Bit manipulation (C++20)
Saturation arithmetic (C++26)
(C++17)
(C++17)
(C++17)
(C++17)
(C++17)
(C++17)
Common mathematical functions
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)(C++11)
(C++11)
(C++11)
Defined in header
<cmath>
(1)
float exp2 ( float num );
(until C++23)
double exp2 ( double num );
/*floating-point-type*/
exp2 ( /*floating-point-type*/ num );
(since C++23) exp2 ( /*floating-point-type*/ num );
(constexpr since C++26)
float exp2f( float num );
(2)
(since C++11) (constexpr since C++26)
long double exp2l( long double num );
(3)
(since C++11) (constexpr since C++26)
SIMD overload (since C++26)
Defined in header
<simd>
template< /*math-floating-point*/ V >
(S)
(since C++26)
constexpr /*deduced-simd-t*/<V>
Additional overloads (since C++11)
Defined in header
<cmath>
template< class Integer >
double exp2 ( Integer num );
(A)
(constexpr since C++26)
double exp2 ( Integer num );
1-3) Computes 2 raised to the given power num. The library provides overloads of
std::exp2 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::exp2 on v_num.- (See math-floating-point and deduced-simd-t for their definitions.)
A) Additional overloads are provided for all integer types, which are treated as double.
(since C++11)[edit] Parameters
num
-
floating-point or integer value
[edit] Return value
If no errors occur, the base-2 exponential of num (2num
) is returned.
If a range error due to overflow occurs, +HUGE_VAL , +HUGE_VALF, or +HUGE_VALL is returned.
If a range error occurs due to underflow, the correct result (after rounding) is returned.
[edit] Error handling
Errors are reported as specified in math_errhandling .
If the implementation supports IEEE floating-point arithmetic (IEC 60559),
- If the argument is ±0, 1 is returned.
- If the argument is -∞, +0 is returned.
- If the argument is +∞, +∞ is returned.
- If the argument is NaN, NaN is returned.
[edit] Notes
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::exp2(num) has the same effect as std::exp2(static_cast<double>(num)).
For integral exponents, it may be preferable to use std::ldexp .
[edit] Example
Run this code
#include <cerrno> #include <cfenv> #include <cmath> #include <cstring> #include <iostream> // #pragma STDC FENV_ACCESS ON int main() { std::cout << "exp2(4) = " << std::exp2(4) << '\n' << "exp2(0.5) = " << std::exp2(0.5) << '\n' << "exp2(-4) = " << std::exp2(-4) << '\n'; // special values std::cout << "exp2(-0) = " << std::exp2(-0.0) << '\n' << "exp2(-Inf) = " << std::exp2(-INFINITY ) << '\n'; // error handling errno = 0; std::feclearexcept (FE_ALL_EXCEPT ); const double inf = std::exp2(1024); const bool is_range_error = errno == ERANGE ; std::cout << "exp2(1024) = " << inf << '\n'; if (is_range_error) std::cout << " errno == ERANGE: " << std::strerror (ERANGE ) << '\n'; if (std::fetestexcept (FE_OVERFLOW )) std::cout << " FE_OVERFLOW raised\n"; }
Possible output:
exp2(4) = 16 exp2(0.5) = 1.41421 exp2(-4) = 0.0625 exp2(-0) = 1 exp2(-Inf) = 0 exp2(1024) = inf errno == ERANGE: Numerical result out of range FE_OVERFLOW raised
[edit] See also
(C++11)(C++11)(C++11)
(function) [edit]
(C++11)(C++11)(C++11)
(function) [edit]
C documentation for exp2