ATAN(3P)

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

✨ ATAN(3P) β€” bestie we're doing arc tangent today ✨

okay so hi 🫢 welcome to the POSIX Programmer's Manual page for ATAN(3P), literally the cutest lil trig function trio you ever did see. Sit down, grab a strawberry πŸ“, we're gonna get you fluent.

πŸ’– PROLOG πŸ’–

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ β€” so bestie, if you're on Linux, go consult the corresponding Linux manual page for the deets on Linux behavior. OR the interface may not even be implemented on Linux at all. πŸ™ˆ iykyk.

πŸ‘‘ NAME πŸ‘‘

atan, atanf, atanl β€” the arc tangent function. three of them. one vibe. periodt.

πŸŽ€ SYNOPSIS πŸŽ€

#include <math.h>

double atan(double x);
float atanf(float x);
long double atanl(long double x);

🌸 DESCRIPTION 🌸

So the functionality described on this reference page is aligned with the ISO C standard. And like β€” any conflict between the requirements described here and the ISO C standard is unintentional, no drama intended fr fr. This volume of POSIX.1‐2017 defers to the ISO C standard. it's giving respectful.

These functions shall compute the principal value of the arc tangent of their argument x. that's the whole job. that's the assignment. πŸ’…

okay and this part is important, bestie β€” if you're an application wishing to check for error situations, you should 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, then an error has occurred. boom. that's the error check. write it down. πŸ“

⭐ RETURN VALUE ⭐

Upon successful completion, these functions shall return the arc tangent of x in the range [-Ο€/2,Ο€/2] radians. cute little window. obsessed.

  • If x is NaN, a NaN shall be returned. πŸ’€
  • If x is Β±0, x shall be returned. (it just hands you back your zero, iconic behavior)
  • If x is Β±Inf, Β±Ο€/2 shall be returned.
  • If x is subnormal, a range error may occur and x should be returned.

And if x is not returned, then atan(), atanf(), and atanl() shall return an implementation-defined value no greater in magnitude than DBL_MIN, FLT_MIN, and LDBL_MIN, respectively. yes, in that order. matching up. slay.

πŸ”₯ ERRORS πŸ”₯

These functions may fail if:

  • Range Error β€” The value of x is subnormal.
    • 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: the tea below is extra, not mandatory πŸ’…)

🌈 EXAMPLES 🌈

None.

that's it. that's the examples section. we got nothing. moving on bestie πŸ¦‹

🧚 APPLICATION USAGE 🧚

On error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each other β€” like two friends who don't text each other, no cap β€” but at least one of them must be non-zero. so they're independent but you can't have neither. boundaries, but make them mandatory. πŸ’œ

πŸ’… RATIONALE πŸ’…

None.

no rationale. we simply do not explain ourselves. main character energy.

🫢 FUTURE DIRECTIONS 🫢

None.

the future is undefined and honestly? we're at peace with it.

✨ SEE ALSO ✨

  • atan2()
  • feclearexcept()
  • fetestexcept()
  • isnan()
  • tan()

And also β€” the Base Definitions volume of POSIX.1‐2017, Section 4.20, Treatment of Error Conditions for Mathematical Functions, and <math.h>. go read those, bestie, they're the lore. πŸ“š

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. (referee. final boss. no arguing.) 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, you ate it, you understood it, you're literally a math.h girlie now πŸŽ€

signing off with love from IEEE/The Open Group, dated 2017, on page ATAN(3P) β€” mwah, go compute some arc tangents πŸ’‹πŸ‘‘

πŸ“¦ where this page comes from