- exponential function
c99 [ flag... ] file... -lm [ library... ] #include <math.h> double exp(double x);
float expf(float x);
long double expl(long double x);
These functions compute the base-e exponential of x.
Upon successful completion, these functions return the exponential value of x.
If the correct value would cause overflow, a range error occurs and exp(), expf(), and expl() return HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.
If x is NaN, a NaN is returned.
If x is ±0, 1 is returned.
If x is +Inf, x is returned.
These functions will fail if:
The result overflows.
If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the overflow floating-point exception is raised.
The exp() function sets errno to ERANGE if the result overflows.
An application wanting to check for exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception has been raised. An application should either examine the return value or check the floating point exception flags to detect exceptions.
An application can also set errno to 0 before calling exp(). On return, if errno is non-zero, an error has occurred. The expf() and expl() functions do not set errno.
See attributes(5) for descriptions of the following attributes: