194 lines
4.5 KiB
HTML
194 lines
4.5 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of ROUND</TITLE>
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</HEAD><BODY>
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<H1>ROUND</H1>
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Section: Linux Programmer's Manual (3)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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round, roundf, roundl - round to nearest integer, away from zero
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<PRE>
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<B>#include <<A HREF="file:///usr/include/math.h">math.h</A>></B>
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<B>double round(double </B><I>x</I><B>);</B>
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<B>float roundf(float </B><I>x</I><B>);</B>
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<B>long double roundl(long double </B><I>x</I><B>);</B>
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</PRE>
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<P>
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Link with <I>-lm</I>.
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<P>
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Feature Test Macro Requirements for glibc (see
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<B><A HREF="/cgi-bin/man/man2html?7+feature_test_macros">feature_test_macros</A></B>(7)):
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<P>
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<B>round</B>(),
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<B>roundf</B>(),
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<B>roundl</B>():
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<DL COMPACT><DT id="1"><DD>
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_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
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</DL>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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These functions round
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<I>x</I>
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to the nearest integer, but
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round halfway cases away from zero (regardless of the current rounding
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direction, see
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<B><A HREF="/cgi-bin/man/man2html?3+fenv">fenv</A></B>(3)),
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instead of to the nearest even integer like
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<B><A HREF="/cgi-bin/man/man2html?3+rint">rint</A></B>(3).
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<P>
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For example,
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<I>round(0.5)</I>
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is 1.0, and
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<I>round(-0.5)</I>
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is -1.0.
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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These functions return the rounded integer value.
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<P>
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If
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<I>x</I>
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is integral, +0, -0, NaN, or infinite,
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<I>x</I>
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itself is returned.
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<A NAME="lbAF"> </A>
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<H2>ERRORS</H2>
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No errors occur.
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POSIX.1-2001 documents a range error for overflows, but see NOTES.
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<A NAME="lbAG"> </A>
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<H2>VERSIONS</H2>
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These functions first appeared in glibc in version 2.1.
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<A NAME="lbAH"> </A>
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<H2>ATTRIBUTES</H2>
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For an explanation of the terms used in this section, see
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<B><A HREF="/cgi-bin/man/man2html?7+attributes">attributes</A></B>(7).
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<TABLE BORDER>
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<TR VALIGN=top><TD><B>Interface</B></TD><TD><B>Attribute</B></TD><TD><B>Value</B><BR></TD></TR>
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<TR VALIGN=top><TD>
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<B>round</B>(),
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<B>roundf</B>(),
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<B>roundl</B>()
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</TD><TD>Thread safety</TD><TD>MT-Safe<BR></TD></TR>
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</TABLE>
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<A NAME="lbAI"> </A>
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<H2>CONFORMING TO</H2>
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C99, POSIX.1-2001, POSIX.1-2008.
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<A NAME="lbAJ"> </A>
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<H2>NOTES</H2>
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POSIX.1-2001 contains text about overflow (which might set
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<I>errno</I>
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to
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<B>ERANGE</B>,
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or raise an
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<B>FE_OVERFLOW</B>
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exception).
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In practice, the result cannot overflow on any current machine,
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so this error-handling stuff is just nonsense.
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(More precisely, overflow can happen only when the maximum value
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of the exponent is smaller than the number of mantissa bits.
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For the IEEE-754 standard 32-bit and 64-bit floating-point numbers
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the maximum value of the exponent is 128 (respectively, 1024),
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and the number of mantissa bits is 24 (respectively, 53).)
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<P>
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If you want to store the rounded value in an integer type,
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you probably want to use one of the functions described in
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<B><A HREF="/cgi-bin/man/man2html?3+lround">lround</A></B>(3)
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instead.
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<A NAME="lbAK"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?3+ceil">ceil</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+floor">floor</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+lround">lround</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+nearbyint">nearbyint</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+rint">rint</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+trunc">trunc</A></B>(3)
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<A NAME="lbAL"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="2"><A HREF="#lbAB">NAME</A><DD>
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<DT id="3"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="4"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="5"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="6"><A HREF="#lbAF">ERRORS</A><DD>
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<DT id="7"><A HREF="#lbAG">VERSIONS</A><DD>
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<DT id="8"><A HREF="#lbAH">ATTRIBUTES</A><DD>
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<DT id="9"><A HREF="#lbAI">CONFORMING TO</A><DD>
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<DT id="10"><A HREF="#lbAJ">NOTES</A><DD>
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<DT id="11"><A HREF="#lbAK">SEE ALSO</A><DD>
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<DT id="12"><A HREF="#lbAL">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:54 GMT, March 31, 2021
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</BODY>
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</HTML>
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