REMAINDER(3P)

💖 PROLOG 💖

okay bestie, real talk before we even start: this manual page is part of the POSIX Programmer's Manual. the Linux implementation of this interface may differ (so like, go check the corresponding Linux manual page for the deets on Linux behavior), or honestly the interface may not be implemented on Linux at all. 🙈 just so you know what you're walking into.

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✨ NAME ✨

remainder, remainderf, remainderl — remainder function 🎀

so yeah, this is the remainder girlies. three of them. a whole squad. and we're in the POSIX Programmer's Manual, section 3P, iykyk.

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🌸 SYNOPSIS 🌸

#include <math.h>

double remainder(double x, double y);
float remainderf(float x, float y);
long double remainderl(long double x, long double y);

look at them. so clean. so iconic. 💅

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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 (not on purpose, bestie, promise). this volume of POSIX.1‐2017 defers to the ISO C standard. periodt.

these functions shall return the floating-point remainder r=x-ny when y is non-zero. the value n is the integral value nearest the exact value x/y. and here's the cute part — when |n-x/y|=½, the value n is chosen to be even. it's giving tie-breaker-to-the-even-number energy. slay.

the behavior of remainder() shall be independent of the rounding mode. no cap. it does not care what mode you're in.

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👑 RETURN VALUE 👑

upon successful completion, these functions shall return the floating-point remainder r=x-ny when y is non-zero.

on systems that do not support the IEC 60559 Floating-Point option, if y is zero, it is implementation-defined whether a domain error occurs or zero is returned. (translation: it depends, bestie, don't @ me.)

if x or y is NaN, a NaN shall be returned.

if x is infinite or y is 0 and the other is non-NaN, 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 ±Inf, or the y argument is ±0 and the other argument is non-NaN.
  • 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:

• Domain Error — the y argument 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.

🫶 heads up: the following sections are informative. like, they're extra lore, not requirements.

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🍓 EXAMPLES 🍓

None.

bestie. literally none. not a single one. 😭

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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. so like, they're doing their own thing, living their own lives, but one of them has to show up to the party. fr fr.

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🧚 RATIONALE 🧚

None.

nothing. nada. the rationale said "no thoughts, head empty." 🙈

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⭐ FUTURE DIRECTIONS ⭐

None.

no future plans babes, this one's settled. 💅

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🔥 SEE ALSO 🔥

• abs()
• div()
• feclearexcept()
• fetestexcept()
• ldiv()

and also the Base Definitions volume of POSIX.1‐2017:

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

go read those too, they're lowkey important. 🎀

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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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and that's the whole page, bestie!! 💖✨🎀🦋🌸💅🫶

this diva of a manual page came to you from IEEE/The Open Group, dated 2017, living her best life as REMAINDER(3P). stay iconic, go do some floating-point math, and remember: when |n-x/y|=½, pick the even one. mwah. 💋