ROUND(P) POSIX Programmer's Manual ROUND(P)NAME
round, roundf, roundl - round to the nearest integer value in a float‐
ing-point format
SYNOPSIS
#include <math.h>
double round(double x);
float roundf(float x);
long double roundl(long double x);
DESCRIPTION
These functions shall round their argument to the nearest integer value
in floating-point format, rounding halfway cases away from zero,
regardless of the current rounding direction.
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.
RETURN VALUE
Upon successful completion, these functions shall return the rounded
integer value.
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 round(), roundf(), and roundl() shall return the value of the macro
±HUGE_VAL, ±HUGE_VALF, and ±HUGE_VALL (with the same sign as x),
respectively.
ERRORS
These functions may fail if:
Range Error
The result overflows.
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.
EXAMPLES
None.
APPLICATION USAGE
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.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSOfeclearexcept() , fetestexcept() , the Base Definitions volume of
IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for
Mathematical Functions, <math.h>
COPYRIGHT
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 original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 ROUND(P)
