FMOD(3P)

💖 FMOD(3P) 💖

okay bestie, welcome to the POSIX Programmer's Manual page for fmod — yes it's a whole vibe, it's from the POSIX Programmer's Manual, and it's giving "I contain multitudes." 🦋

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🌸 PROLOG 🌸

so like, heads up before we even start: 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 💅

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✨ NAME ✨

fmod, fmodf, fmodl — floating-point remainder value function. it's the math girlies' moment fr fr 🎀

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🫶 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);

look at those three icons. one for the doubles, one for the floats, one for the long doubles. equity. 👑

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💜 DESCRIPTION 💜

okay so, important context 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. This volume of POSIX.1‐2017 defers to the ISO C standard. so if you see a fight, ISO C wins, no drama. 🤝

These functions shall return the floating-point remainder of the division of x by y. that's it. that's the whole job. 💖

An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred. basically: wipe the slate clean, then vibe check it after. 🌈

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🎀 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. it's subtraction, but make it fashion. 💅

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() in there, I'm not touching it, that's the source material, periodt.) 😭

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 now" and honestly? fair. ✨

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.

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🔥 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.

The following sections are informative. (translation: the drama is over, the rest is just lore 🧚)

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🌟 EXAMPLES 🌟

None. literally nothing. empty. a clean girl aesthetic moment. 🕊️

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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. they're not codependent besties, but one of them HAS to show up to the function. 😤

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🌈 RATIONALE 🌈

None. no thoughts, head empty, iconic. 🦋

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⭐ FUTURE DIRECTIONS ⭐

None. the future is undefined but this section is not. 💅

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👑 SEE ALSO 👑

• feclearexcept()
• fetestexcept()
• isnan()
• 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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okay that's the whole page, you ate it, you understood it, slay. 🫶✨

this came to you courtesy of IEEE/The Open Group, dated 2017, and it's FMOD(3P) — go forth and take remainders, bestie. 💅🎀