EXP2(3P)

📦 version 2017a, in alpine 3.22, alpine 3.23, alpine 3.24, arch rolling, nixpkgs unstable, opensuse-leap 16.0

💖 EXP2(3P) — POSIX Programmer's Manual 💖

okay bestie, welcome to the POSIX Programmer's Manual section for exp2. this is your girl explaining exponential-base-2 functions and i am so hype about it. let's gooo ✨

🌸 PROLOG 🌸

okay so before literally anything else: 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 — plot twist — the interface may not be implemented on Linux at all. 💀

✨ NAME ✨

exp2, exp2f, exp2l — exponential base 2 functions. that's it, that's the name, we move.

🎀 SYNOPSIS 🎀

#include <math.h>

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

💅 DESCRIPTION 💅

okay so real talk, 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 — no drama intended fr. this volume of POSIX.1‐2017 defers to the ISO C standard. periodt.

These functions shall compute the base-2 exponential of x. yes, base 2. iconic behavior.

An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. Then on return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred. that's your vibe check right there. 🔍

👑 RETURN VALUE 👑

Upon successful completion, these functions shall return 2<sup>x</sup> (the original writes it as 2x, and yes bestie, that's exponentiation in the original's flat text, keep it in mind).

  • 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.

🔥 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.

The following sections are informative. (translation: cute bonus content, not binding 💖)

🦋 EXAMPLES 🦋

None.

literally nothing. the void. an empty plate. we stan a minimal queen. 🙈

🌈 APPLICATION USAGE 🌈

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. iykyk. 👑

⭐ RATIONALE ⭐

None.

🧚 FUTURE DIRECTIONS 🧚

None.

💜 SEE ALSO 💜

  • exp()
  • feclearexcept()
  • fetestexcept()
  • isnan()
  • log()

Also, from The Base Definitions volume of POSIX.1‐2017:

  • Section 4.20, Treatment of Error Conditions for Mathematical Functions
  • <math.h>

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 .

okay that's the whole page bestie, no cap, every single detail preserved 💖

and that's a wrap, gorgeous — this one's brought to you by IEEE/The Open Group, dated 2017, page EXP2(3P). go forth and compute base-2 exponentials responsibly 🫶✨

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