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| .TH ROUND 3 2017-09-15 "" "Linux Programmer's Manual" |
| .SH NAME |
| round, roundf, roundl \- round to nearest integer, away from zero |
| .SH SYNOPSIS |
| .nf |
| .B #include <math.h> |
| .PP |
| .BI "double round(double " x ); |
| .BI "float roundf(float " x ); |
| .BI "long double roundl(long double " x ); |
| .fi |
| .PP |
| Link with \fI\-lm\fP. |
| .PP |
| .in -4n |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .in |
| .PP |
| .ad l |
| .BR round (), |
| .BR roundf (), |
| .BR roundl (): |
| .RS 4 |
| _ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L |
| .RE |
| .ad |
| .SH DESCRIPTION |
| These functions round |
| .I x |
| to the nearest integer, but |
| round halfway cases away from zero (regardless of the current rounding |
| direction, see |
| .BR fenv (3)), |
| instead of to the nearest even integer like |
| .BR rint (3). |
| .PP |
| For example, |
| .IR round(0.5) |
| is 1.0, and |
| .IR round(\-0.5) |
| is \-1.0. |
| .SH RETURN VALUE |
| These functions return the rounded integer value. |
| .PP |
| If |
| .I x |
| is integral, +0, \-0, NaN, or infinite, |
| .I x |
| itself is returned. |
| .SH ERRORS |
| No errors occur. |
| POSIX.1-2001 documents a range error for overflows, but see NOTES. |
| .SH VERSIONS |
| These functions first appeared in glibc in version 2.1. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .TS |
| allbox; |
| lbw27 lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR round (), |
| .BR roundf (), |
| .BR roundl () |
| T} Thread safety MT-Safe |
| .TE |
| .SH CONFORMING TO |
| C99, POSIX.1-2001, POSIX.1-2008. |
| .SH NOTES |
| POSIX.1-2001 contains text about overflow (which might set |
| .I errno |
| to |
| .BR ERANGE , |
| or raise an |
| .B FE_OVERFLOW |
| exception). |
| In practice, the result cannot overflow on any current machine, |
| so this error-handling stuff is just nonsense. |
| .\" The POSIX.1-2001 APPLICATION USAGE SECTION discusses this point. |
| (More precisely, overflow can happen only when the maximum value |
| of the exponent is smaller than the number of mantissa bits. |
| For the IEEE-754 standard 32-bit and 64-bit floating-point numbers |
| the maximum value of the exponent is 128 (respectively, 1024), |
| and the number of mantissa bits is 24 (respectively, 53).) |
| .PP |
| If you want to store the rounded value in an integer type, |
| you probably want to use one of the functions described in |
| .BR lround (3) |
| instead. |
| .SH SEE ALSO |
| .BR ceil (3), |
| .BR floor (3), |
| .BR lround (3), |
| .BR nearbyint (3), |
| .BR rint (3), |
| .BR trunc (3) |