EXP2(3) Library Functions Manual EXP2(3)

exp2 exp2f exp2l — exponential base 2 functions

#include <math.h>

double exp2(double x);
float exp2f(float x);
long double exp2l(long double x);

The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2008 defers to the ISO C standard.

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 (FE_ALL_EXCEPT) before calling these functions. On return, if errno is non-zero or (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 (), (), and () 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 [MX] either 0.0 (if supported), or an implementation-defined value shall be returned.

[MX] 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:

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:

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.

None.

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

None.

None.

exp(3) , feclearexcept(3) , fetestexcept(3) , isnan(3) , log(3)

XBD V1_chap04(7) , <math.h>

First released in Issue 6. Derived from the ISO/IEC 9899:1999 (“ISO C99”) standard.

January 1, 2008 posix.fail