**#include <math.h>
**

**
double exp2(double** *x***);
float exp2f(float**

long double exp2l(long double

These functions shall compute the base-2 exponential of *x*.

An application wishing to check for error situations should set *errno*
to zero and call
*feclearexcept*(FE_ALL_EXCEPT) before calling these functions.
On return, if *errno* is non-zero or
*fetestexcept*(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW)
is non-zero, an error has occurred.

Upon successful completion, these functions shall return 2***x*.

If the correct value would cause overflow, a range error shall occur
and *exp2*(), *exp2f*(), and *exp2l*() shall
return the value of the macro HUGE_VAL, HUGE_VALF, and HUGE_VALL,
respectively.

If the correct value would cause underflow, and is not representable, a range error may occur, and either 0.0 (if supported), or an implementation-defined value shall be returned.

If
*x* is NaN, a NaN shall be returned.

If *x* is ±0, 1 shall be returned.

If *x* is -Inf, +0 shall be returned.

If *x* is +Inf, *x* shall be returned.

If the correct value would cause underflow, and is representable, a range error may occur and the correct value shall be returned.

These functions shall fail if:

- Range Error
- The result overflows.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
then *errno* shall be set to [ERANGE]. If the
integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
then the overflow floating-point exception shall be
raised.

These functions may fail if:

- Range Error
- The result underflows.

If the integer expression (math_errhandling & MATH_ERRNO) is non-zero,
then *errno* shall be set to [ERANGE]. If the
integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero,
then the underflow floating-point exception shall be
raised.

*The following sections are informative.*

For IEEE Std 754-1985 **double**, 1024 <= *x* implies *exp2*(
*x*) has overflowed. The value
*x* < -1022 implies *exp*( *x*) has underflowed.

On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero.

*exp*() , *feclearexcept*() , *fetestexcept*() , *isnan*()
, *log*() , the
Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment
of Error Conditions for Mathematical Functions, *<math.h>*

- NAME
- SYNOPSIS
- DESCRIPTION
- RETURN VALUE
- ERRORS
- EXAMPLES
- APPLICATION USAGE
- RATIONALE
- FUTURE DIRECTIONS
- SEE ALSO
- COPYRIGHT

Time: 21:45:46 GMT, April 16, 2011