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

Since C++26

Header: <cmath>

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)

# Declarations

float exp2 ( float num );
double exp2 ( double num );
long double exp2 ( long double num );

(until C++23)

/*floating-point-type*/
exp2 ( /*floating-point-type*/ num );

(since C++23) (constexpr since C++26)

float exp2f( float num );

(since C++11) (constexpr since C++26)

long double exp2l( long double num );

(since C++11) (constexpr since C++26)

SIMD overload (since C++26)

template< /*math-floating-point*/ V >
constexpr /*deduced-simd-t*/<V>
exp2 ( const V& v_num );

(since C++26)

Additional overloads (since C++11)

template< class Integer >
double exp2 ( Integer num );

(constexpr since C++26)

# Parameters

# Return value

If no errors occur, the base-2 exponential of num (2num) is returned.

# 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(num)).

For integral exponents, it may be preferable to use std::ldexp.

# 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 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";
}

# See also