ROUND(P) POSIX Programmer's Manual ROUND(P)
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 direc-
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 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 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 ROUND(P)