The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2004 Edition
Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.
A newer edition of this document exists here


remainder, remainderf, remainderl - remainder function


#include <math.h>

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


[CX] [Option Start] 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 IEEE Std 1003.1-2001 defers to the ISO C standard. [Option End]

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.


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

[MX] [Option Start] 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 either a NaN (if supported), or an implementation-defined value shall be returned. [Option End]


These functions shall fail if:

Domain Error
[MX] [Option Start] 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. [Option End]

The following sections are informative.




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.






abs(), div(), feclearexcept(), fetestexcept(), ldiv(), the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for Mathematical Functions, <math.h>


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.

End of informative text.

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