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.1-2017 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 (), 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, [MXX] and is not representable, a range error may occur, and exp2 (), exp2f (), and exp2l () shall return [MXX] 0.0, or (if the IEC 60559 Floating-Point option is not supported) an implementation-defined value no greater in magnitude than DBL_MIN, FLT_MIN, and LDBL_MIN, respectively.

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.

[MXX] 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.

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.

POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0108 [68] and XSH/TC1-2008/0109 [68] are applied.

POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0102 [630] is applied.

January 31, 2018 posix.fail