| <html lang="en"> |
| <head> |
| <title>Absolute Value - The GNU C Library</title> |
| <meta http-equiv="Content-Type" content="text/html"> |
| <meta name="description" content="The GNU C Library"> |
| <meta name="generator" content="makeinfo 4.13"> |
| <link title="Top" rel="start" href="index.html#Top"> |
| <link rel="up" href="Arithmetic-Functions.html#Arithmetic-Functions" title="Arithmetic Functions"> |
| <link rel="next" href="Normalization-Functions.html#Normalization-Functions" title="Normalization Functions"> |
| <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> |
| <!-- |
| This file documents the GNU C library. |
| |
| This is Edition 0.12, last updated 2007-10-27, |
| of `The GNU C Library Reference Manual', for version |
| 2.8 (Sourcery G++ Lite 2011.03-41). |
| |
| Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2001, 2002, |
| 2003, 2007, 2008, 2010 Free Software Foundation, Inc. |
| |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the GNU Free Documentation License, Version 1.3 or |
| any later version published by the Free Software Foundation; with the |
| Invariant Sections being ``Free Software Needs Free Documentation'' |
| and ``GNU Lesser General Public License'', the Front-Cover texts being |
| ``A GNU Manual'', and with the Back-Cover Texts as in (a) below. A |
| copy of the license is included in the section entitled "GNU Free |
| Documentation License". |
| |
| (a) The FSF's Back-Cover Text is: ``You have the freedom to |
| copy and modify this GNU manual. Buying copies from the FSF |
| supports it in developing GNU and promoting software freedom.''--> |
| <meta http-equiv="Content-Style-Type" content="text/css"> |
| <style type="text/css"><!-- |
| pre.display { font-family:inherit } |
| pre.format { font-family:inherit } |
| pre.smalldisplay { font-family:inherit; font-size:smaller } |
| pre.smallformat { font-family:inherit; font-size:smaller } |
| pre.smallexample { font-size:smaller } |
| pre.smalllisp { font-size:smaller } |
| span.sc { font-variant:small-caps } |
| span.roman { font-family:serif; font-weight:normal; } |
| span.sansserif { font-family:sans-serif; font-weight:normal; } |
| --></style> |
| <link rel="stylesheet" type="text/css" href="../cs.css"> |
| </head> |
| <body> |
| <div class="node"> |
| <a name="Absolute-Value"></a> |
| <p> |
| Next: <a rel="next" accesskey="n" href="Normalization-Functions.html#Normalization-Functions">Normalization Functions</a>, |
| Up: <a rel="up" accesskey="u" href="Arithmetic-Functions.html#Arithmetic-Functions">Arithmetic Functions</a> |
| <hr> |
| </div> |
| |
| <h4 class="subsection">20.8.1 Absolute Value</h4> |
| |
| <p><a name="index-absolute-value-functions-2404"></a> |
| These functions are provided for obtaining the <dfn>absolute value</dfn> (or |
| <dfn>magnitude</dfn>) of a number. The absolute value of a real number |
| <var>x</var> is <var>x</var> if <var>x</var> is positive, −<var>x</var> if <var>x</var> is |
| negative. For a complex number <var>z</var>, whose real part is <var>x</var> and |
| whose imaginary part is <var>y</var>, the absolute value is <code>sqrt (</code><var>x</var><code>*</code><var>x</var><code> + </code><var>y</var><code>*</code><var>y</var><code>)</code><!-- /@w -->. |
| |
| <p><a name="index-math_002eh-2405"></a><a name="index-stdlib_002eh-2406"></a>Prototypes for <code>abs</code>, <code>labs</code> and <code>llabs</code> are in <samp><span class="file">stdlib.h</span></samp>; |
| <code>imaxabs</code> is declared in <samp><span class="file">inttypes.h</span></samp>; |
| <code>fabs</code>, <code>fabsf</code> and <code>fabsl</code> are declared in <samp><span class="file">math.h</span></samp>. |
| <code>cabs</code>, <code>cabsf</code> and <code>cabsl</code> are declared in <samp><span class="file">complex.h</span></samp>. |
| |
| <!-- stdlib.h --> |
| <!-- ISO --> |
| <div class="defun"> |
| — Function: int <b>abs</b> (<var>int number</var>)<var><a name="index-abs-2407"></a></var><br> |
| <blockquote><!-- stdlib.h --> |
| <!-- ISO --> |
| — Function: long int <b>labs</b> (<var>long int number</var>)<var><a name="index-labs-2408"></a></var><br> |
| <blockquote><!-- stdlib.h --> |
| <!-- ISO --> |
| — Function: long long int <b>llabs</b> (<var>long long int number</var>)<var><a name="index-llabs-2409"></a></var><br> |
| <blockquote><!-- inttypes.h --> |
| <!-- ISO --> |
| — Function: intmax_t <b>imaxabs</b> (<var>intmax_t number</var>)<var><a name="index-imaxabs-2410"></a></var><br> |
| <blockquote><p>These functions return the absolute value of <var>number</var>. |
| |
| <p>Most computers use a two's complement integer representation, in which |
| the absolute value of <code>INT_MIN</code> (the smallest possible <code>int</code>) |
| cannot be represented; thus, <code>abs (INT_MIN)</code><!-- /@w --> is not defined. |
| |
| <p><code>llabs</code> and <code>imaxdiv</code> are new to ISO C99<!-- /@w -->. |
| |
| <p>See <a href="Integers.html#Integers">Integers</a> for a description of the <code>intmax_t</code> type. |
| |
| </blockquote></div> |
| |
| <!-- math.h --> |
| <!-- ISO --> |
| <div class="defun"> |
| — Function: double <b>fabs</b> (<var>double number</var>)<var><a name="index-fabs-2411"></a></var><br> |
| <blockquote><!-- math.h --> |
| <!-- ISO --> |
| — Function: float <b>fabsf</b> (<var>float number</var>)<var><a name="index-fabsf-2412"></a></var><br> |
| <blockquote><!-- math.h --> |
| <!-- ISO --> |
| — Function: long double <b>fabsl</b> (<var>long double number</var>)<var><a name="index-fabsl-2413"></a></var><br> |
| <blockquote><p>This function returns the absolute value of the floating-point number |
| <var>number</var>. |
| </p></blockquote></div> |
| |
| <!-- complex.h --> |
| <!-- ISO --> |
| <div class="defun"> |
| — Function: double <b>cabs</b> (<var>complex double z</var>)<var><a name="index-cabs-2414"></a></var><br> |
| <blockquote><!-- complex.h --> |
| <!-- ISO --> |
| — Function: float <b>cabsf</b> (<var>complex float z</var>)<var><a name="index-cabsf-2415"></a></var><br> |
| <blockquote><!-- complex.h --> |
| <!-- ISO --> |
| — Function: long double <b>cabsl</b> (<var>complex long double z</var>)<var><a name="index-cabsl-2416"></a></var><br> |
| <blockquote><p>These functions return the absolute value of the complex number <var>z</var> |
| (see <a href="Complex-Numbers.html#Complex-Numbers">Complex Numbers</a>). The absolute value of a complex number is: |
| |
| <pre class="smallexample"> sqrt (creal (<var>z</var>) * creal (<var>z</var>) + cimag (<var>z</var>) * cimag (<var>z</var>)) |
| </pre> |
| <p>This function should always be used instead of the direct formula |
| because it takes special care to avoid losing precision. It may also |
| take advantage of hardware support for this operation. See <code>hypot</code> |
| in <a href="Exponents-and-Logarithms.html#Exponents-and-Logarithms">Exponents and Logarithms</a>. |
| </p></blockquote></div> |
| |
| </body></html> |
| |
