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std::exp, std::expf, std::expl

From cppreference.com
< cpp‎ | numeric‎ | math
 
 
 
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Defined in header <cmath>
(1)
float       exp ( float arg );
float       expf( float arg );
(since C++11)
double      exp ( double arg );
(2)
(3)
long double exp ( long double arg );
long double expl( long double arg );
(since C++11)
double      exp ( IntegralType arg );
(4) (since C++11)
1-3) Computes 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).

Contents

[edit] Parameters

arg - value of floating-point or Integral type

[edit] 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.

[edit] 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

[edit] Notes

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

[edit] Example

#include <iostream>
#include <iomanip>
#include <cmath>
#include <cerrno>
#include <cstring>
#include <cfenv>
#pragma STDC FENV_ACCESS ON
int main()
{
    std::cout << "exp(1) = e¹ = " << std::setprecision(16) << std::exp(1) << '\n'
              << "FV of $100, continuously compounded at 3% for 1 year = "
              << std::setprecision(6) << 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) = e¹ = 2.718281828459045
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

[edit] See also

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