# std::exp

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< cpp‎ | numeric‎ | math

Defined in header `<cmath>` |  |
float exp( float arg ); | (1) |
double exp( double arg ); | (2) |
long double exp( long double arg ); | (3) |
double exp( Integral arg ); | (4) | (since C++11)

Computes the e (Euler's number, `2.7182818`) raised to the given power `arg`

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

arg | - | value of floating-point or Integral type

### Return value

If no errors occur, the base-e exponential of `arg` (earg
) 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

For IEEE-compatible type double, overflow is guaranteed if 709.8 < arg, and underflow is guaranteed if arg < -708.4

### Example

Run this code

    #include <iostream>
    #include <cmath>
    #include <cerrno>
    #include <cstring>
    #include <cfenv>
    #pragma STDC FENV_ACCESS ON
    int main()
    {
        std::cout << "exp(1) = " << std::exp(1) << '\n'
                  << "FV of $100, continuously compounded at 3% for 1 year = "
                  << 100*std::exp(0.03) << '\n';
        // special values
        std::cout << "exp(-0) = " << std::exp(-0.0) << '\n'
                  << "exp(-Inf) = " << std::exp(-INFINITY) << '\n';
        // error handling
        errno=0; std::feclearexcept(FE_ALL_EXCEPT);
        std::cout << "exp(710) = " << std::exp(710) << '\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:

    exp(1) = 2.71828
    FV of $100, continuously compounded at 3% for 1 year = 103.045
    exp(-0) = 1
    exp(-Inf) = 0
    exp(710) = inf
        errno == ERANGE: Numerical result out of range
        FE_OVERFLOW raised

### See also

exp2 (C++11) | returns 2 raised to the given power (2x) (function)
expm1 (C++11) | returns e raised to the given power, minus one (ex-1) (function)
log | computes natural (base e) logarithm (to base e) (ln(x)) (function)
exp(std::complex) | complex base e exponential (function template)
exp(std::valarray) | applies the function std::exp to each element of valarray (function template)
C documentation for exp

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