NAME¶

std::exp2,std::exp2f,std::exp2l - std::exp2,std::exp2f,std::exp2l

Synopsis¶

Defined in header <cmath>
float exp2 ( float n ); (1) (since C++11)
float exp2f( float n );
double exp2 ( double n ); (2) (since C++11)
long double exp2 ( long double n ); (3) (since C++11)
long double exp2l( long double n );
double exp2 ( IntegralType n ); (4) (since C++11)

1-3) Computes 2 raised to the given power n
4) A set of overloads or a function template accepting an argument of any integral
type. Equivalent to (2) (the argument is cast to double).

Parameters¶

n - value of floating-point or Integral type

Return value¶

If no errors occur, the base-2 exponential of n (2n
) 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

Example¶

// Run this code

#include <iostream>
#include <cmath>
#include <cerrno>
#include <cstring>
#include <cfenv>
// #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";
}

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

See also¶

exp
expf returns e raised to the given power (\({\small e^x}\)e^x)
expl (function)
(C++11)
(C++11)
expm1
expm1f
expm1l returns e raised to the given power, minus one (\({\small e^x-1}\)e^x-1)
(C++11) (function)
(C++11)
(C++11)
log2
log2f
log2l base 2 logarithm of the given number (\({\small \log_{2}{x} }\)log[2](x))
(C++11) (function)
(C++11)
(C++11)