Exp
Defined in header <cmath>
.
Description
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 num
Declarations
- C++23
- C++11
// 1)
/* floating-point-type */ exp2( /* floating-point-type */ num );
// 2)
float exp2f( float num );
// 3)
long double exp2l( long double num );
// 4)
template< class Integer >
double exp2 ( Integer num );
// 1)
float exp2 ( float num );
// 2)
double exp2 ( double num );
// 3)
long double exp2 ( long double num );
// 4)
float exp2f( float num );
// 5)
long double exp2l( long double num );
// 6)
template< class Integer >
double exp2 ( Integer num );
Parameters
num
- floating-point or integer value
Return value
If no errors occur, the base-2 exponential of num
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.
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
Notes
The additional overloads are not required to be provided exactly as Additional Overloads.
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))
.
Examples
#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);
std::cout
<< "exp2(1024) = "
<< std::exp2(1024) << '\n';
if (errno == ERANGE)
std::cout
<< "errno == ERANGE: "
<< std::strerror(errno) << '\n';
if (std::fetestexcept(FE_OVERFLOW))
std::cout
<< "FE_OVERFLOW raised\n";
}
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