#include <math.h> float expf(float x);
expf computes the base-e exponential of x.
If |x| >~ 88.722, errno is set to EDOM and expf returns HUGE_VALF.
If x is NaN, expf returns NaN.
If x is ∞, expf returns ∞
If x is -∞, expf returns 0.
expf conforms to ISO/IEC 9899:1990 (C90) and ISO/IEC 9899:1999 (C99).