REMQUO(3POSIX)

💖 REMQUO — bestie's guide to the remainder girlies 💖

okay so real talk, this page is from the POSIX Programmer's Manual, and I need you to know something before we go any further:

PROLOG — listen up fr fr 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.

like. it might not even be on your Linux box. vibe check accordingly 💀

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✨ NAME ✨

remquo, remquof, remquol — the remainder functions, but make it quotient-flavored 🎀

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🦋 SYNOPSIS 🦋

#include <math.h>

double remquo(double x, double y, int *quo);
float remquof(float x, float y, int *quo);
long double remquol(long double x, long double y, int *quo);

three flavors, one for each size of float. she's versatile like that 💅

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🌸 DESCRIPTION 🌸

First things first, bestie, some legal-ish tea:

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.

periodt. the standard is the standard.

So what do these girlies actually DO? remquo(), remquof(), and remquol() shall compute the same remainder as the remainder(), remainderf(), and remainderl() functions, respectively. same math, no cap.

BUT. and this is the iconic part ✨ — in the object pointed to by quo, they store a value whose sign is the sign of x/y and whose magnitude is congruent modulo 2n to the magnitude of the integral quotient of x/y, where n is an implementation-defined integer greater than or equal to 3.

(read that one again if you need to, it's giving math class but we move 🫶)

And if y is zero? the value stored in the object pointed to by quo is unspecified. like, we don't know her. she's a mystery.

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okay now, if you're the type of bestie who wants to check for error situations — and honestly you should be — here's the ritual:

• set errno to zero
• call feclearexcept(FE_ALL_EXCEPT) before calling these functions

then on return, if errno is non-zero or 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 👑

These functions shall return x REM y. that's it, that's the whole vibe.

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. (so like, depends on the system. read the room.)

If x or y is NaN, a NaN shall be returned. NaN in, NaN out, iconic behavior 💀

If x is ±Inf or y is zero and the other argument 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. (translation: they're the bonus content, not the requirements.)

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🍓 EXAMPLES 🍓

None.

...yeah. nothing. she said no examples today, and honestly? respect the boundaries 🙈

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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 a package deal, but somebody has to show up to the function 💜

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⭐ RATIONALE ⭐

These functions are intended for implementing argument reductions which can exploit a few low-order bits of the quotient.

Note that x may be so large in magnitude relative to y that an exact representation of the quotient is not practical. so don't come for her about precision, she's doing her best 😭

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🌈 FUTURE DIRECTIONS 🌈

None.

she's not going anywhere. she's staying exactly like this. main character stability 👑

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🫶 SEE ALSO 🫶

• feclearexcept()
• fetestexcept()
• remainder()

And from the Base Definitions volume of POSIX.1‐2017:

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

iykyk 💖

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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 bestie that's the whole page, we ate and left no crumbs 🎀

IEEE/The Open Group — 2017 — REMQUO(3POSIX) ✨ bye pookie, go compute some remainders 💅