EXP2(3POSIX)

🫶 PROLOG 🫶

Okay bestie, real talk first: this manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (so like, go consult the corresponding Linux manual page for the deets on Linux behavior), or honestly the interface may not even be implemented on Linux at all. Vibe check accordingly. 💅

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✨ NAME ✨

exp2, exp2f, exp2l — exponential base 2 functions 🌸

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🎀 SYNOPSIS 🎀

#include <math.h>

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

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💖 DESCRIPTION 💖

So the functionality described on this reference page is aligned with the ISO C standard. If there's any conflict between what's required here and what the ISO C standard says, that's unintentional — no drama intended. This volume of POSIX.1‐2017 defers to the ISO C standard, periodt.

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

Now, if your application wants to check for error situations, here's the move: set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. Then on return, if errno is non-zero, or if fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred. That's the whole vibe check right there. 🔥

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🌈 RETURN VALUE 🌈

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

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 exp2(), exp2f(), and exp2l() shall return 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.

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

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💀 ERRORS 💀

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.

Heads up bestie: the following sections are informative. 👀

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🍓 EXAMPLES 🍓

None. 😭 (not me hoping for a little example... there is none. moving on.)

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🦋 APPLICATION USAGE 🦋

On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each other — like, they don't text each other, they don't share a group chat — but at least one of them must be non-zero. No cap.

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🧚 RATIONALE 🧚

None. 🙈

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⭐ FUTURE DIRECTIONS ⭐

None. 💅

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👑 SEE ALSO 👑

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

The Base Definitions volume of POSIX.1‐2017, Section 4.20, Treatment of Error Conditions for Mathematical Functions, <math.h>

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💜 COPYRIGHT 💜

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

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And that's the whole page, bestie!! 🎀 This icon of a manual was served up by IEEE/The Open Group, dated 2017, and it lives under the name EXP2(3POSIX) in the POSIX Programmer's Manual. Stan a math function. 💅✨