The Open Group Base Specifications Issue 7
IEEE Std 1003.1, 2013 Edition
Copyright © 2001-2013 The IEEE and The Open Group

#### NAME

> remainder, remainderf, remainderl - remainder function

#### 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`);
> ``

#### DESCRIPTION

> [CX] 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.

> 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. When |n-x/y|=½, the value n is chosen to be even.

> The behavior of remainder() shall be independent of the rounding mode.

#### 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.

> [MX] 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.

#### ERRORS

> These functions shall fail if:

> Domain Error
>   [MX] 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.

#### EXAMPLES

> None.

#### 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

> None.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> abs, div, feclearexcept, fetestexcept, ldiv

> XBD Treatment of Error Conditions for Mathematical Functions, <math.h>

#### CHANGE HISTORY

> First released in Issue 4, Version 2.

#### Issue 5

> Moved from X/OPEN UNIX extension to BASE.

#### Issue 6

> The remainder() function is no longer marked as an extension.

> The remainderf() and remainderl() functions are added for alignment with the ISO/IEC 9899:1999 standard.

> The DESCRIPTION, RETURN VALUE, ERRORS, and APPLICATION USAGE sections are revised to align with the ISO/IEC 9899:1999 standard.

> IEC 60559:1989 standard floating-point extensions over the ISO/IEC 9899:1999 standard are marked.

#### Issue 7

> ISO/IEC 9899:1999 standard, Technical Corrigendum 2 #55 (SD5-XSH-ERN-82) is applied.

> POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0506 [320] is applied.

End of informative text.

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