# remquo man page

## Prolog

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.

remquo, remquof, remquol — remainder functions

## 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*);

## Description

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.1‐2008 defers to the ISO C standard.

The *remquo*(), *remquof*(), and *remquol*() functions shall compute the same remainder as the *remainder*(), *remainderf*(), and *remainderl*() functions, respectively. 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 2^{n} to the magnitude of the integral quotient of *x*/*y*, where *n* is an implementation-defined integer greater than or equal to 3. If *y* is zero, the value stored in the object pointed to by *quo* is unspecified.

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.

## Return Value

These functions shall return *x* REM *y*.

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.

If *x* or *y* is NaN, a NaN shall be returned.

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.

## 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.

*The following sections are informative.*

## 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.

## 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.

## See Also

*feclearexcept()*, *fetestexcept()*, *remainder()*

The Base Definitions volume of POSIX.1‐2008, *Section 4.19*, *Treatment of Error Conditions for Mathematical Functions*, **<math.h>**

## Copyright

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .