ROUND(3P) POSIX Programmer's Manual ROUND(3P)
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the correspond-
ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.
round, roundf, roundl - round to the nearest integer value in a floating-point format
double round(double x);
float roundf(float x);
long double roundl(long double x);
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
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.
These functions may fail if:
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.
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.
feclearexcept(), fetestexcept(), the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.18, Treatment of Error Conditions for Math-
ematical Functions, <math.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
ogy -- 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 .
/The Open Group 2003 ROUND(3P)