ACOSH(3POSIX)

💖 ACOSH(3POSIX) — the POSIX Programmer's Manual, bestie edition 💖

okay so before we even get into it, a little prolog tea ☕:

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

so like, this is the POSIX spec version, not necessarily your Linux box's version. check your local manpage if you wanna know what your machine is actually doing. 🫶

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✨ NAME ✨

acosh, acoshf, acoshl — inverse hyperbolic cosine functions 🌸

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🌈 SYNOPSIS 🌈

#include <math.h>

double acosh(double x);
float acoshf(float x);
long double acoshl(long double x);

three flavors, three precision levels, all doing the same lil trick 💅

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🎀 DESCRIPTION 🎀

okay first, the fine print: 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. (so if they ever beef, ISO C wins, no cap.)

these functions shall compute the inverse hyperbolic cosine of their argument x. that's the whole job. main character energy, honestly.

now — if your application wants to check for error situations (and honestly, icon behavior), here's the ritual: 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 — bestie, an error has occurred. 😭

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💅 RETURN VALUE 💅

upon successful completion, these functions shall return the inverse hyperbolic cosine of their argument. slay.

but here's where it gets spicy 🔥:

• for finite values of x < 1, a domain error shall occur, and either a NaN (if supported), or an implementation-defined value shall be returned.
• if x is NaN, a NaN shall be returned.
• if x is +1, +0 shall be returned.
• if x is +Inf, +Inf shall be returned.
• if x is -Inf, a domain error shall occur, and a NaN shall be returned.

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🚨 ERRORS 🚨

these functions shall fail if:

Domain Error 💀

the x argument is finite and less than +1.0, or is -Inf.

if the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [EDOM]. if the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shall be raised.

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The following sections are informative. 👑 (yes that's literally what the spec says, we're in the informative zone now, it's giving bonus content)

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🍓 EXAMPLES 🍓

None.

(not me leaving this section empty, it's what the spec said, i don't make the rules 💀)

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🧚 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. ✨

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🌸 RATIONALE 🌸

None.

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🦋 FUTURE DIRECTIONS 🦋

None.

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⭐ SEE ALSO ⭐

• cosh()
• feclearexcept()
• fetestexcept()

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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that's the whole page bestie, courtesy of IEEE/The Open Group, dating all the way back to 2017 — and yes, that's the footer, we mention it cute and we move on 💖✨🎀