std::exp, std::expf, std::expl
Defined in header <cmath> | ||
| (1) | ||
float exp (float num ); double exp (double num ); | (until C++23) | |
/*floating-point-type*/ exp (/*floating-point-type*/ num ); | (since C++23) (constexpr since C++26) | |
float expf(float num ); | (2) | (since C++11) (constexpr since C++26) |
longdouble expl(longdouble num ); | (3) | (since C++11) (constexpr since C++26) |
SIMD overload(since C++26) | ||
Defined in header <simd> | ||
template</*math-floating-point*/ V > constexpr/*deduced-simd-t*/<V> | (S) | (since C++26) |
Additional overloads(since C++11) | ||
Defined in header <cmath> | ||
template<class Integer > double exp ( Integer num ); | (A) | (constexpr since C++26) |
std::exp for all cv-unqualified floating-point types as the type of the parameter.(since C++23)S) The SIMD overload performs an element-wise std::exp on v_num.
| (since C++26) |
A) Additional overloads are provided for all integer types, which are treated as double. | (since C++11) |
Contents |
[edit]Parameters
| num | - | floating-point or integer value |
[edit]Return value
If no errors occur, the base-e exponential of num (enum
) is returned.
If a range error occurs due to overflow, +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 < num, and underflow is guaranteed if num < -708.4.
The additional overloads are not required to be provided exactly as (A). 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)).
[edit]Example
#include <cerrno>#include <cfenv>#include <cmath>#include <cstring>#include <iomanip>#include <iostream>#include <numbers> // #pragma STDC FENV_ACCESS ON consteval double approx_e(){longdouble e{1.0};for(auto fac{1ull}, n{1llu}; n !=18;++n, fac *= n) e +=1.0/ fac;return e;} int main(){std::cout<<std::setprecision(16)<<"exp(1) = e¹ = "<< std::exp(1)<<'\n'<<"numbers::e = "<<std::numbers::e<<'\n'<<"approx_e = "<< approx_e()<<'\n'<<"FV of $100, continuously compounded at 3% for 1 year = "<<std::setprecision(6)<<100* std::exp(0.03)<<'\n'; // special valuesstd::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 numbers::e = 2.718281828459045 approx_e = 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) |
(C++11)(C++11)(C++11) | returns e raised to the given power, minus 1 (ex-1) (function) |
(C++11)(C++11) | computes natural (base e) logarithm (ln(x)) (function) |
| complex base e exponential (function template) | |
| applies the function std::exp to each element of valarray (function template) | |
C documentation for exp | |
