exp2, exp2f, exp2l - compute exponential function

Syntax	#include <math.h> double exp2(double x); C11 float exp2f(float x); long double exp2l(long double x); (End)
Description	These functions compute the exponential function to the base 2 for a permitted floating-point number x
Return val.	2x	if successful.
	HUGE_VAL HUGE_VALF HUGE_VALL	depending on the function type, if an overflow occurs. errno is set to indicate the error.
Errors	exp(), expf() and expl() will fail if
	ERANGE	Overflow; the return value is too high.
See also	exp(), log(), log2(), log10(), pow(), math.h.