Calculate the base2 exponential of a number
Synopsis:
#include <math.h>
double exp2( double x );
float exp2f( float x );
long double exp2l(long double x );
Arguments:
 x
 The number that you want to calculate the base2 exponential of.
Library:
libm
Use the l m option to
qcc
to link against this library.
Description:
The exp2(), exp2f(), and exp2l() functions
compute the base2 exponential function of x (i.e., 2^{x}).
To check for error situations, use
feclearexcept()
and
fetestexcept():
 Call feclearexcept(FE_ALL_EXCEPT) before calling
exp2(), exp2f(), or exp2l().
 On return, if fetestexcept(FE_INVALID  FE_DIVBYZERO  FE_OVERFLOW  FE_UNDERFLOW)
is nonzero, then an error has occurred.
Returns:
The base2 exponential function of x.
 If the correct value would cause overflow, a range error occurs, and these function return
HUGE_VAL, HUGE_VALF, and HUGE_VALL, respectively.
 If the correct value would cause an underflow, a range error may occur, and these functions return 0.
 If x is NaN, NaN is returned.
 If x is ±0, 1 is returned.
 If x is Inf, +0 is returned.
 If x is +Inf, x is returned.
 If the correct value would cause an underflow and is representable, a range error may occur,
and the correct value is returned.
Errors:
 FE_OVERFLOW
 The result overflows.
 FE_UNDERFLOW
 The result underflows.
Classification:
ANSI,
POSIX 1003.1
Safety: 

Cancellation point 
No 
Interrupt handler 
No 
Signal handler 
No 
Thread 
Yes 