IEEE Std 1003.1-2008, 2016 Edition

Copyright © 2001-2016 The IEEE and The Open Group

rint, rintf, rintl - round-to-nearest integral value

#include <math.h>

double rint(doublex);

float rintf(floatx);

long double rintl(long doublex);

^{[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 integral value (represented as a

double) nearestxin the direction of the current rounding mode. The current rounding mode is implementation-defined.If the current rounding mode rounds toward negative infinity, then

rint() shall be equivalent tofloor. If the current rounding mode rounds toward positive infinity, thenrint() shall be equivalent toceil. If the current rounding mode rounds towards zero, thenrint() shall be equivalent totrunc.^{[MX]}If the current rounding mode rounds towards nearest, thenrint() differs fromroundin that halfway cases are rounded to even rather than away from zero.These functions differ from the

nearbyint(),nearbyintf(), andnearbyintl() functions only in that they may raise the inexact floating-point exception if the result differs in value from the argument.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.

Upon successful completion, these functions shall return the integer (represented as a double precision number) nearest

xin the direction of the current rounding mode.^{[MX]}The result shall have the same sign asx.

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

xis ±0 or ±Inf,xshall be returned.

No errors are defined.

None.

The integral value returned by these functions need not be expressible as an

intmax_t. The return value should be tested before assigning it to an integer type to avoid the undefined results of an integer overflow.

None.

None.

abs,ceil,feclearexcept,fetestexcept,floor,isnan,nearbyintXBD

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

First released in Issue 4, Version 2.

Moved from X/OPEN UNIX extension to BASE.

The following changes are made for alignment with the ISO/IEC 9899:1999 standard:

The

rintf() andrintl() functions are added.The

rint() function is no longer marked as an extension.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/TC1-2008/0514 [346], XSH/TC1-2008/0515 [346], XSH/TC1-2008/0516 [346], XSH/TC1-2008/0517 [346], and XSH/TC1-2008/0518 [346] are applied.

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