FMOD(3POSIX)

📦 version 2017a, in debian bookworm, debian trixie, ubuntu jammy, ubuntu noble, ubuntu resolute, ubuntu stonking

✨ FMOD(3POSIX) ✨

okay so bestie, real talk: this is the POSIX Programmer's Manual page for fmod and the girlies. It lives in the family of FMOD(3POSIX) man pages, and before we even get going:

⚠️ heads up ⚠️ 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 the interface may not be implemented on Linux at all. crying. 😭

🌸 PROLOG 🌸

as stated above, bestie: 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. iykyk 💅

🎀 NAME 🎀

fmod, fmodf, fmodl — the floating-point remainder value function. that's the whole vibe. one job, done flawlessly. 👑

🦋 SYNOPSIS 🦋

#include <math.h>

double fmod(double x, double y);
float fmodf(float x, float y);
long double fmodl(long double x, long double y);

three flavors, same energy: double, float, long double. pick your girl. ✨

💖 DESCRIPTION 💖

first things first, the legality of it all: 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 drama, we don't make the rules.)

These functions shall return the floating-point remainder of the division of x by y. math but make it ✨serve✨

and if you're the kind of bestie who wants to actually check for error situations, here's the ritual: set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. 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. vibe check failed. 🙈

🔥 RETURN VALUE 🔥

These functions shall return the value x-i*y, for some integer i such that, if y is non-zero, the result has the same sign as x and magnitude less than the magnitude of y. iconic behavior honestly.

If the correct value would cause underflow, and is not representable, a range error may occur, and fmod(), modf(), and fmodl() 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. yes it says modf(), we do not ask questions, we report the facts. 💀

the special-case lore, in order:

  • If x or y is NaN, a NaN shall be returned, and none of the conditions below shall be considered. (NaN said "I'm the main character" and we respect it.)
  • If y is zero, a domain error shall occur, and a NaN shall be returned.
  • If x is infinite, a domain error shall occur, and a NaN shall be returned.
  • If x is ±0 and y is not zero, ±0 shall be returned.
  • If x is not infinite and y 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.
🛑 note it: infinite x or zero y = domain error = NaN. that's not a suggestion, that's the law.

👑 ERRORS 👑

These functions shall fail if:

Domain Error

The x argument is infinite or y is zero.

  • 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.

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.

and then, bestie… the following sections are informative. which is fancy speak for "not the binding part, just the tea." ☕

🌈 EXAMPLES 🌈

None.

literally nothing. the void. the absence. <em>the nothingness.</em> 🕳️✨

🫶 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. they're not a couple, they're just roommates, but one of them has to pay rent. 💅

🧚 RATIONALE 🧚

None.

no thoughts, head empty, nothing to justify. 🎀

⭐ FUTURE DIRECTIONS ⭐

None.

the future is… nothing. <em>slay.</em> 🔮

💜 SEE ALSO 💜

  • feclearexcept()
  • fetestexcept()
  • isnan()
  • Section 4.20, Treatment of Error Conditions for Mathematical Functions, <math.h>

go read those too, bestie, they're the supporting cast. 🌸

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 .

and that's the whole page, bestie!! 🎉 this one came to you from IEEE/The Open Group, dated 2017, filed under FMOD(3POSIX). drink some water, check your errno, and go take the remainder of your day. 💖✨🦋

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