IEEE Std 1003.1, 2013 Edition

Copyright © 2001-2013 The IEEE and The Open Group

exp2, exp2f, exp2l - exponential base 2 functions

#include <math.h>

double exp2(doublex);

float exp2f(floatx);

long double exp2l(long doublex);

^{[CX]}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

errnoto zero and callfeclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, iferrnois non-zero orfetestexcept(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(), andexp2l() 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, andexp2(),exp2f(), andexp2l() 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.

^{[MX]}Ifxis NaN, a NaN shall be returned.If

xis ±0, 1 shall be returned.If

xis -Inf, +0 shall be returned.If

xis +Inf,xshall 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:

- Range Error
- The result overflows.
If the integer expression (

math_errhandling& MATH_ERRNO) is non-zero, thenerrnoshall 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, thenerrnoshall 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

double, 1024 <=ximpliesexp2(x) has overflowed. The valuex< -1022 impliesexp(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,feclearexcept,fetestexcept,isnan,logXBD

Treatment of Error Conditions for Mathematical Functions,<math.h>

First released in Issue 6. Derived from the ISO/IEC 9899:1999 standard.

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

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