std::exp2

Defined in header <cmath>

1	`double` `exp2(` `double` `n );`

(1)

(since C++11)

1	`float` `exp2(` `float` `n );`

(2)

(since C++11)

1	`long` `double` `exp2(` `long` `double` `n );`

(3)

(since C++11)

1	`double` `exp2( Integral 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

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

#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

exp	returns e raised to the given power (e^x) (function)
expm1 (C++11)	returns e raised to the given power, minus one (e^x-1) (function)
log2 (C++11)	base 2 logarithm of the given number (log₂(x)) (function)
C documentation for `exp2`

std::exp2

Parameters

Return value

Error handling

Example

See also