IEEE Std 1003.1-2017 (Revision of IEEE Std 1003.1-2008)

Copyright © 2001-2018 IEEE and The Open Group

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 POSIX.1-2017 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,

^{[MXX]}and is not representable, a range error may occur, andfmod(),modf(), andfmodl() shall return^{[MXX]}0.0, or (if the IEC 60559 Floating-Point option is not supported) an implementation-defined value no greater in magnitude than DBL_MIN, FLT_MIN, and LDBL_MIN, respectively.

^{[MX]}Ifxoryis NaN, a NaN shall be returned, and none of the conditions below shall be considered.If

yis zero, a domain error shall occur, and a NaN shall be returned.If

xis infinite, a domain error shall occur, and a NaN shall be returned.If

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

xis not infinite andyis ±Inf,xshall be returned.

^{[MXX]}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, thenerrnoshall 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, thenerrnoshall 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

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.

POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0151 [68], XSH/TC1-2008/0152 [320], and XSH/TC1-2008/0153 [68] are applied.

POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0120 [605] is applied.

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