IEEE Std 1003.1, 2004 Edition

Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.

fmod, fmodf, fmodl - floating-point remainder value function

#include <math.h>

double fmod(doublex, doubley);

float fmodf(floatx, floaty);

long double fmodl(long doublex, long doubley);

^{[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 IEEE Std 1003.1-2001 defers to the ISO C standard.These functions shall return the floating-point remainder of the division of

xbyy.An application wishing to check for error situations should set

errnoto zero and callfeclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, iferrnois non-zero orfetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

These functions shall return the value

x-i*y, for some integerisuch that, ifyis non-zero, the result has the same sign asxand magnitude less than the magnitude ofy.If the correct value would cause underflow, and is not representable, a range error may occur, and

^{[MX]}either 0.0 (if supported), or an implementation-defined value shall be returned.

^{[MX]}Ifxoryis NaN, a NaN shall be returned.If

yis zero, a domain error shall occur, and either a NaN (if supported), or an implementation-defined value shall be returned.If

xis infinite, a domain error shall occur, and either a NaN (if supported), or an implementation-defined value shall be returned.If

xis ±0 andyis not zero, ±0 shall be returned.If

xis not infinite andyis ±Inf,xshall be returned.If the correct value would cause underflow, and is representable, a range error may occur and the correct value shall be returned.

These functions shall fail if:

- Domain Error
^{[MX]}Thexargument is infinite oryis zero.If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then

errnoshall 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

errnoshall be set to [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the underflow floating-point exception shall be raised.

None.

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.

None.

None.

feclearexcept(),fetestexcept(),isnan(), 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 1. Derived from Issue 1 of the SVID.

The DESCRIPTION is updated to indicate how an application should check for an error. This text was previously published in the APPLICATION USAGE section.

The behavior for when the

yargument is zero is now defined.The

fmodf() andfmodl() 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.

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