Exp
Defined in header <cmath>
.
Description
Computes e
(Euler's number, 2.7182818...) raised to the given power num
.
The library provides overloads of std::exp
for all cv-unqualified floating-point types as the type of the parameter num
.
Declarations
- C++23
- C++11
// 1)
/* floating-point-type */ exp( /* floating-point-type */ num );
// 2)
float expf( float num );
// 3)
long double expl( long double num );
// 4)
template< class Integer >
double exp ( Integer num );
// 1)
float exp ( float num );
// 2)
double exp ( double num );
// 3)
long double exp ( long double num );
// 4)
float expf( float num );
// 5)
long double expl( long double num );
// 6)
template< class Integer >
double exp ( Integer num );
Parameters
num
- floating-point or integer value
Return value
If no errors occur, the base-e exponential of num
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 < num
, and underflow is guaranteed if num < -708.4
.
The additional overloads are not required to be provided exactly as Additional Overloads.
They only need to be sufficient to ensure that for their argument num of integer type,
std::exp(num)
has the same effect as std::exp(static_cast<double>(num))
.
Examples
#include <cerrno>
#include <cfenv>
#include <cmath>
#include <cstring>
#include <iostream>
#include <iomanip>
// #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";
}
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