Updated: April 19, 2023 |
Compute the exponential function of a number
#include <math.h> double exp( double x ); float expf( float x ); long double expl( long double x );
Your system requirements will determine how you should work with these libraries:
These functions compute the exponential function of x (i.e., e^{x}).
To check for error situations, use feclearexcept() and fetestexcept(). For example:
The exponential value of x.
If x is: | These functions return: | Errors: |
---|---|---|
±0.0 | 1 | — |
A value that would cause overflow | Inf | FE_OVERFLOW |
A value that would cause underflow | 0.0 | FE_UNDERFLOW |
-Inf | 0.0 | — |
Inf | Inf | — |
NaN | NaN | — |
These functions raise FE_INEXACT if the FPU reports that the result can't be exactly represented as a floating-point number.
#include <stdio.h> #include <math.h> #include <fenv.h> #include <stdlib.h> int main( void ) { int except_flags; feclearexcept(FE_ALL_EXCEPT); printf( "%f\n", exp(.5) ); except_flags = fetestexcept(FE_ALL_EXCEPT); if(except_flags) { /* An error occurred; handle it appropriately. */ } return EXIT_SUCCESS; }
produces the output:
1.648721
Safety: | |
---|---|
Cancellation point | No |
Interrupt handler | Yes |
Signal handler | Yes |
Thread | Yes |
The value of expm1(x) may be more accurate than exp(x) - 1.0 for small values of x.