ACOSH(3P)

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

okay bestie, so this is page ACOSH(3P) from the POSIX Programmer's Manual, and we're about to get so cozy with the inverse hyperbolic cosine functions. pull up a chair, grab a boba, let's go 🧋✨

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🌸 PROLOG 🌸

so like, heads up first: this manual page is part of the POSIX Programmer's Manual. the Linux implementation of this interface may differ (so pls consult the corresponding Linux manual page for the deets on Linux behavior), or honestly the interface might not even be implemented on Linux at all. no cap. 🙈

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✨ NAME ✨

acosh, acoshf, acoshl — the inverse hyperbolic cosine functions, aka the math girlies 💅

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🎀 SYNOPSIS 🎀

#include <math.h>

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

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🦋 DESCRIPTION 🦋

okay so first things first, 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 (we're not trying to start drama fr). this volume of POSIX.1‐2017 defers to the ISO C standard.

these functions shall compute the inverse hyperbolic cosine of their argument x. iconic behavior honestly.

now, an application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. that's the pre-game ritual bestie. 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. slay, you caught it. 🔥

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💜 RETURN VALUE 💜

upon successful completion, these functions shall return the inverse hyperbolic cosine of their argument. simple as that. 💖

• 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.

the following sections are informative. (so like, the lore, not the law 🫶)

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🌈 EXAMPLES 🌈

None. — yeah bestie, there's literally nothing here. the void. the silence. 💀

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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 two besties living their own lives — but at least one of them must be non-zero. that part is not optional, okay? periodt.

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🧚 RATIONALE 🧚

None. — nothing to see here, moving on, no thoughts head empty. 🍓

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👑 FUTURE DIRECTIONS 👑

None. — the future is a mystery, but this page is not changing. 💅

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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 originals are the main characters here, we're just the group chat 🫶) 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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okay that's the whole page bestie!! 💅✨ this one's brought to you by IEEE/The Open Group, 2017 — like, the original drop, the vintage queen 👑. stay hydrated, set your errno to zero, and remember: if x is -Inf, we do NOT return a number, we return NaN and a domain error, and that's just the rules babe. mwah 💋🎀🦋