std::exp2, std::exp2f, std::exp2l
Defined in header <cmath> | ||
| (1) | ||
float exp2 (float num ); double exp2 (double num ); | (until C++23) | |
/*floating-point-type*/ exp2 (/*floating-point-type*/ num ); | (since C++23) (constexpr since C++26) | |
float exp2f(float num ); | (2) | (since C++11) (constexpr since C++26) |
longdouble exp2l(longdouble num ); | (3) | (since C++11) (constexpr since C++26) |
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 exp2 ( Integer num ); | (A) | (constexpr since C++26) |
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.
| (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
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
#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 valuesstd::cout<<"exp2(-0) = "<< std::exp2(-0.0)<<'\n'<<"exp2(-Inf) = "<< std::exp2(-INFINITY)<<'\n'; // error handlingerrno=0;std::feclearexcept(FE_ALL_EXCEPT);constdouble inf = std::exp2(1024);constbool 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) | returns e raised to the given power (ex) (function) |
(C++11)(C++11)(C++11) | returns e raised to the given power, minus 1 (ex-1) (function) |
(C++11)(C++11) | multiplies a number by 2 raised to an integral power (function) |
(C++11)(C++11)(C++11) | base 2 logarithm of the given number (log2(x)) (function) |
C documentation for exp2 | |
