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

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< cpp‎ | numeric‎ | math

Defined in header `<cmath>` |  |
float exp2 ( float n ); float exp2f( float n ); | (1) | (since C++11)
double exp2 ( double n ); | (2) | (since C++11)
long double exp2 ( long double n ); long double exp2l( long double n ); | (3) | (since C++11)
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 expl (C++11)(C++11) | returns e raised to the given power (ex) (function)
expm1 expm1f expm1l (C++11)(C++11)(C++11) | returns e raised to the given power, minus one (ex-1) (function)
log2 log2f log2l (C++11)(C++11)(C++11) | base 2 logarithm of the given number (log2(x)) (function)

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