RINT(P) POSIX Programmer's Manual RINT(P)
rint, rintf, rintl - round-to-nearest integral value
double rint(double x);
float rintf(float x);
long double rintl(long double x);
These functions shall return the integral value (represented as a double) nearest x in the
direction of the current rounding mode. The current rounding mode is implementation-
If the current rounding mode rounds toward negative infinity, then rint() shall be equiva-
lent to floor() . If the current rounding mode rounds toward positive infinity, then
rint() shall be equivalent to ceil() .
These functions differ from the nearbyint(), nearbyintf(), and nearbyintl() 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 errno to zero and call
feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if errno is non-
zero or fetestexcept(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 x in the direction of the current rounding mode.
If x is NaN, a NaN shall be returned.
If x is +-0 or +-Inf, x shall be returned.
If the correct value would cause overflow, a range error shall occur and rint(), rintf(),
and rintl() shall return the value of the macro +-HUGE_VAL, +-HUGE_VALF, and +-HUGE_VALL
(with the same sign as x), respectively.
These functions shall fail if:
The result would cause an overflow.
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be
set to [ERANGE]. If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-
zero, then the overflow floating-point exception shall be raised.
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() , ceil() , feclearexcept() , fetestexcept() , floor() , isnan() , nearbyint() , the
Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Condi-
tions for Mathematical Functions, <math.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and The Open Group
Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 RINT(P)