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<center><font size="2">The Open Group Base Specifications Issue 6<br>
IEEE Std 1003.1-2001<br>
Copyright &copy; 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<hr size="2" noshade>
<h4><a name="tag_13_26_01"></a>NAME</h4>
<blockquote>math.h - mathematical declarations</blockquote>
<h4><a name="tag_13_26_02"></a>SYNOPSIS</h4>
<blockquote class="synopsis">
<p><tt>#include &lt;math.h&gt;</tt></p>
</blockquote>
<h4><a name="tag_13_26_03"></a>DESCRIPTION</h4>
<blockquote>
<div class="box"><sup>[<a href="javascript:open_code('CX')">CX</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]"
border="0"> Some of the functionality described on this reference page extends the ISO&nbsp;C standard. Applications shall define
the appropriate feature test macro (see the System Interfaces volume of IEEE&nbsp;Std&nbsp;1003.1-2001, <a href=
"../functions/xsh_chap02_02.html">Section 2.2, The Compilation Environment</a>) to enable the visibility of these symbols in this
header. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></div>
<p>The <i>&lt;math.h&gt;</i> header shall include definitions for at least the following types:</p>
<dl compact>
<dt><b>float_t</b></dt>
<dd>A real-floating type at least as wide as <b>float</b>.</dd>
<dt><b>double_t</b></dt>
<dd>A real-floating type at least as wide as <b>double</b>, and at least as wide as <b>float_t</b>.</dd>
</dl>
<p>If FLT_EVAL_METHOD equals 0, <b>float_t</b> and <b>double_t</b> shall be <b>float</b> and <b>double</b>, respectively; if
FLT_EVAL_METHOD equals 1, they shall both be <b>double</b>; if FLT_EVAL_METHOD equals 2, they shall both be <b>long double</b>; for
other values of FLT_EVAL_METHOD, they are otherwise implementation-defined.</p>
<p>The <i>&lt;math.h&gt;</i> header shall define the following macros, where real-floating indicates that the argument shall be an
expression of real-floating type:</p>
<pre>
<tt>int fpclassify(real-floating x);
int isfinite(real-floating x);
int isinf(real-floating x);
int isnan(real-floating x);
int isnormal(real-floating x);
int signbit(real-floating x);
int isgreater(real-floating x, real-floating y);
int isgreaterequal(real-floating x, real-floating y);
int isless(real-floating x, real-floating y);
int islessequal(real-floating x, real-floating y);
int islessgreater(real-floating x, real-floating y);
int isunordered(real-floating x, real-floating y);
</tt>
</pre>
<p>The <i>&lt;math.h&gt;</i> header shall provide for the following constants. The values are of type <b>double</b> and are
accurate within the precision of the <b>double</b> type.</p>
<dl compact>
<dt>M_E</dt>
<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
Value of <i>e</i></dd>
<dt>M_LOG2E</dt>
<dd>Value of log<small><sub>2</sub></small><i>e</i></dd>
<dt>M_LOG10E</dt>
<dd>Value of log<small><sub>10</sub></small><i>e</i></dd>
<dt>M_LN2</dt>
<dd>Value of log<small><sub>e</sub></small>2</dd>
<dt>M_LN10</dt>
<dd>Value of log<small><sub>e</sub></small>10</dd>
<dt>M_PI</dt>
<dd>Value of <sub><img src="../images/pi.gif"></sub></dd>
<dt>M_PI_2</dt>
<dd>Value of <sub><img src="../images/pi.gif"></sub>/2</dd>
<dt>M_PI_4</dt>
<dd>Value of <sub><img src="../images/pi.gif"></sub>/4</dd>
<dt>M_1_PI</dt>
<dd>Value of 1/<sub><img src="../images/pi.gif"></sub></dd>
<dt>M_2_PI</dt>
<dd>Value of 2/<sub><img src="../images/pi.gif"></sub></dd>
<dt>M_2_SQRTPI</dt>
<dd>Value of 2/ <sub><img src="../images/sqrt2.gif"><img src="../images/pi.gif"></sub></dd>
<dt>M_SQRT2</dt>
<dd>Value of <sub><img src="../images/sqrt2.gif"></sub>2</dd>
<dt>M_SQRT1_2</dt>
<dd>Value of 1/<sub><img src="../images/sqrt2.gif"></sub>2 <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd>
</dl>
<p>The header shall define the following symbolic constants:</p>
<dl compact>
<dt>MAXFLOAT</dt>
<dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
Value of maximum non-infinite single-precision floating-point number. <img src="../images/opt-end.gif" alt="[Option End]" border=
"0"></dd>
<dt>HUGE_VAL</dt>
<dd>A positive <b>double</b> expression, not necessarily representable as a <b>float</b>. Used as an error value returned by the
mathematics library. HUGE_VAL evaluates to +infinity on systems supporting IEEE&nbsp;Std&nbsp;754-1985.</dd>
<dt>HUGE_VALF</dt>
<dd>A positive <b>float</b> constant expression. Used as an error value returned by the mathematics library. HUGE_VALF evaluates to
+infinity on systems supporting IEEE&nbsp;Std&nbsp;754-1985.</dd>
<dt>HUGE_VALL</dt>
<dd>A positive <b>long double</b> constant expression. Used as an error value returned by the mathematics library. HUGE_VALL
evaluates to +infinity on systems supporting IEEE&nbsp;Std&nbsp;754-1985.</dd>
<dt>INFINITY</dt>
<dd>A constant expression of type <b>float</b> representing positive or unsigned infinity, if available; else a positive constant
of type <b>float</b> that overflows at translation time.</dd>
<dt>NAN</dt>
<dd>A constant expression of type <b>float</b> representing a quiet NaN. This symbolic constant is only defined if the
implementation supports quiet NaNs for the <b>float</b> type.</dd>
</dl>
<p>The following macros shall be defined for number classification. They represent the mutually-exclusive kinds of floating-point
values. They expand to integer constant expressions with distinct values. Additional implementation-defined floating-point
classifications, with macro definitions beginning with FP_ and an uppercase letter, may also be specified by the
implementation.</p>
<blockquote>
<pre>
FP_INFINITE
FP_NAN
FP_NORMAL
FP_SUBNORMAL
FP_ZERO
</pre>
</blockquote>
<p>The following optional macros indicate whether the <a href="../functions/fma.html"><i>fma</i>()</a> family of functions are fast
compared with direct code:</p>
<blockquote>
<pre>
FP_FAST_FMA
FP_FAST_FMAF
FP_FAST_FMAL
</pre>
</blockquote>
<p>The FP_FAST_FMA macro shall be defined to indicate that the <a href="../functions/fma.html"><i>fma</i>()</a> function generally
executes about as fast as, or faster than, a multiply and an add of <b>double</b> operands. The other macros have the equivalent
meaning for the <b>float</b> and <b>long double</b> versions.</p>
<p>The following macros shall expand to integer constant expressions whose values are returned by <i>ilogb</i>( <i>x</i>) if
<i>x</i> is zero or NaN, respectively. The value of FP_ILOGB0 shall be either {INT_MIN} or - {INT_MAX}. The value of FP_ILOGBNAN
shall be either {INT_MAX} or {INT_MIN}.</p>
<blockquote>
<pre>
FP_ILOGB0
FP_ILOGBNAN
</pre>
</blockquote>
<p>The following macros shall expand to the integer constants 1 and 2, respectively;</p>
<blockquote>
<pre>
MATH_ERRNO
MATH_ERREXCEPT
</pre>
</blockquote>
<p>The following macro shall expand to an expression that has type <b>int</b> and the value MATH_ERRNO, MATH_ERREXCEPT, or the
bitwise-inclusive OR of both:</p>
<blockquote>
<pre>
math_errhandling
</pre>
</blockquote>
<p>The value of math_errhandling is constant for the duration of the program. It is unspecified whether math_errhandling is a macro
or an identifier with external linkage. If a macro definition is suppressed or a program defines an identifier with the name
math_errhandling , the behavior is undefined. If the expression (math_errhandling &amp; MATH_ERREXCEPT) can be non-zero, the
implementation shall define the macros FE_DIVBYZERO, FE_INVALID, and FE_OVERFLOW in <a href=
"../basedefs/fenv.h.html"><i>&lt;fenv.h&gt;</i></a>.</p>
<p>The following shall be declared as functions and may also be defined as macros. Function prototypes shall be provided.</p>
<pre>
<tt>double acos(double);
float acosf(float);
double acosh(double);
float acoshf(float);
long double acoshl(long double);
long double acosl(long double);
double asin(double);
float asinf(float);
double asinh(double);
float asinhf(float);
long double asinhl(long double);
long double asinl(long double);
double atan(double);
double atan2(double, double);
float atan2f(float, float);
long double atan2l(long double, long double);
float atanf(float);
double atanh(double);
float atanhf(float);
long double atanhl(long double);
long double atanl(long double);
double cbrt(double);
float cbrtf(float);
long double cbrtl(long double);
double ceil(double);
float ceilf(float);
long double ceill(long double);
double copysign(double, double);
float copysignf(float, float);
long double copysignl(long double, long double);
double cos(double);
float cosf(float);
double cosh(double);
float coshf(float);
long double coshl(long double);
long double cosl(long double);
double erf(double);
double erfc(double);
float erfcf(float);
long double erfcl(long double);
float erff(float);
long double erfl(long double);
double exp(double);
double exp2(double);
float exp2f(float);
long double exp2l(long double);
float expf(float);
long double expl(long double);
double expm1(double);
float expm1f(float);
long double expm1l(long double);
double fabs(double);
float fabsf(float);
long double fabsl(long double);
double fdim(double, double);
float fdimf(float, float);
long double fdiml(long double, long double);
double floor(double);
float floorf(float);
long double floorl(long double);
double fma(double, double, double);
float fmaf(float, float, float);
long double fmal(long double, long double, long double);
double fmax(double, double);
float fmaxf(float, float);
long double fmaxl(long double, long double);
double fmin(double, double);
float fminf(float, float);
long double fminl(long double, long double);
double fmod(double, double);
float fmodf(float, float);
long double fmodl(long double, long double);
double frexp(double, int *);
float frexpf(float value, int *);
long double frexpl(long double value, int *);
double hypot(double, double);
float hypotf(float, float);
long double hypotl(long double, long double);
int ilogb(double);
int ilogbf(float);
int ilogbl(long double);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
double j0(double);
double j1(double);
double jn(int, double);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
double ldexp(double, int);
float ldexpf(float, int);
long double ldexpl(long double, int);
double lgamma(double);
float lgammaf(float);
long double lgammal(long double);
long long llrint(double);
long long llrintf(float);
long long llrintl(long double);
long long llround(double);
long long llroundf(float);
long long llroundl(long double);
double log(double);
double log10(double);
float log10f(float);
long double log10l(long double);
double log1p(double);
float log1pf(float);
long double log1pl(long double);
double log2(double);
float log2f(float);
long double log2l(long double);
double logb(double);
float logbf(float);
long double logbl(long double);
float logf(float);
long double logl(long double);
long lrint(double);
long lrintf(float);
long lrintl(long double);
long lround(double);
long lroundf(float);
long lroundl(long double);
double modf(double, double *);
float modff(float, float *);
long double modfl(long double, long double *);
double nan(const char *);
float nanf(const char *);
long double nanl(const char *);
double nearbyint(double);
float nearbyintf(float);
long double nearbyintl(long double);
double nextafter(double, double);
float nextafterf(float, float);
long double nextafterl(long double, long double);
double nexttoward(double, long double);
float nexttowardf(float, long double);
long double nexttowardl(long double, long double);
double pow(double, double);
float powf(float, float);
long double powl(long double, long double);
double remainder(double, double);
float remainderf(float, float);
long double remainderl(long double, long double);
double remquo(double, double, int *);
float remquof(float, float, int *);
long double remquol(long double, long double, int *);
double rint(double);
float rintf(float);
long double rintl(long double);
double round(double);
float roundf(float);
long double roundl(long double);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
double scalb(double, double);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
double scalbln(double, long);
float scalblnf(float, long);
long double scalblnl(long double, long);
double scalbn(double, int);
float scalbnf(float, int);
long double scalbnl(long double, int);
double sin(double);
float sinf(float);
double sinh(double);
float sinhf(float);
long double sinhl(long double);
long double sinl(long double);
double sqrt(double);
float sqrtf(float);
long double sqrtl(long double);
double tan(double);
float tanf(float);
double tanh(double);
float tanhf(float);
long double tanhl(long double);
long double tanl(long double);
double tgamma(double);
float tgammaf(float);
long double tgammal(long double);
double trunc(double);
float truncf(float);
long double truncl(long double);
<sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
double y0(double);
double y1(double);
double yn(int, double);
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
</tt>
</pre>
<p>The following external variable shall be defined:</p>
<pre>
<tt><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup><img src="../images/opt-start.gif" alt="[Option Start]" border="0">
extern int signgam;
<img src="../images/opt-end.gif" alt="[Option End]" border="0">
</tt>
</pre>
<p>The behavior of each of the functions defined in <i>&lt;math.h&gt;</i> is specified in the System Interfaces volume of
IEEE&nbsp;Std&nbsp;1003.1-2001 for all representable values of its input arguments, except where stated otherwise. Each function
shall execute as if it were a single operation without generating any externally visible exceptional conditions.</p>
</blockquote>
<hr>
<div class="box"><em>The following sections are informative.</em></div>
<h4><a name="tag_13_26_04"></a>APPLICATION USAGE</h4>
<blockquote>
<p>The FP_CONTRACT pragma can be used to allow (if the state is on) or disallow (if the state is off) the implementation to
contract expressions. Each pragma can occur either outside external declarations or preceding all explicit declarations and
statements inside a compound statement. When outside external declarations, the pragma takes effect from its occurrence until
another FP_CONTRACT pragma is encountered, or until the end of the translation unit. When inside a compound statement, the pragma
takes effect from its occurrence until another FP_CONTRACT pragma is encountered (including within a nested compound statement), or
until the end of the compound statement; at the end of a compound statement the state for the pragma is restored to its condition
just before the compound statement. If this pragma is used in any other context, the behavior is undefined. The default state (on
or off) for the pragma is implementation-defined.</p>
</blockquote>
<h4><a name="tag_13_26_05"></a>RATIONALE</h4>
<blockquote>
<p>Before the ISO/IEC&nbsp;9899:1999 standard, the math library was defined only for the floating type <b>double</b>. All the names
formed by appending <tt>'f'</tt> or <tt>'l'</tt> to a name in <i>&lt;math.h&gt;</i> were reserved to allow for the definition of
<b>float</b> and <b>long double</b> libraries; and the ISO/IEC&nbsp;9899:1999 standard provides for all three versions of math
functions.</p>
<p>The functions <a href="../functions/ecvt.html"><i>ecvt</i>()</a>, <a href="../functions/fcvt.html"><i>fcvt</i>()</a>, and <a
href="../functions/gcvt.html"><i>gcvt</i>()</a> have been dropped from the ISO&nbsp;C standard since their capability is available
through <a href="../functions/sprintf.html"><i>sprintf</i>()</a>. These are provided on XSI-conformant systems supporting the
Legacy Option Group.</p>
</blockquote>
<h4><a name="tag_13_26_06"></a>FUTURE DIRECTIONS</h4>
<blockquote>
<p>None.</p>
</blockquote>
<h4><a name="tag_13_26_07"></a>SEE ALSO</h4>
<blockquote>
<p><a href="stddef.h.html"><i>&lt;stddef.h&gt;</i></a> , <a href="sys/types.h.html"><i>&lt;sys/types.h&gt;</i></a> , the System
Interfaces volume of IEEE&nbsp;Std&nbsp;1003.1-2001, <a href="../functions/acos.html"><i>acos</i>()</a>, <a href=
"../functions/acosh.html"><i>acosh</i>()</a>, <a href="../functions/asin.html"><i>asin</i>()</a>, <a href=
"../functions/atan.html"><i>atan</i>()</a>, <a href="../functions/atan2.html"><i>atan2</i>()</a>, <a href=
"../functions/cbrt.html"><i>cbrt</i>()</a>, <a href="../functions/ceil.html"><i>ceil</i>()</a>, <a href=
"../functions/cos.html"><i>cos</i>()</a>, <a href="../functions/cosh.html"><i>cosh</i>()</a>, <a href=
"../functions/erf.html"><i>erf</i>()</a>, <a href="../functions/exp.html"><i>exp</i>()</a>, <a href=
"../functions/expm1.html"><i>expm1</i>()</a>, <a href="../functions/fabs.html"><i>fabs</i>()</a>, <a href=
"../functions/floor.html"><i>floor</i>()</a>, <a href="../functions/fmod.html"><i>fmod</i>()</a>, <a href=
"../functions/frexp.html"><i>frexp</i>()</a>, <a href="../functions/hypot.html"><i>hypot</i>()</a>, <a href=
"../functions/ilogb.html"><i>ilogb</i>()</a>, <a href="../functions/isnan.html"><i>isnan</i>()</a>, <a href=
"../functions/j0.html"><i>j0</i>()</a>, <a href="../functions/ldexp.html"><i>ldexp</i>()</a>, <a href=
"../functions/lgamma.html"><i>lgamma</i>()</a>, <a href="../functions/log.html"><i>log</i>()</a>, <a href=
"../functions/log10.html"><i>log10</i>()</a>, <a href="../functions/log1p.html"><i>log1p</i>()</a>, <a href=
"../functions/logb.html"><i>logb</i>()</a>, <a href="../functions/modf.html"><i>modf</i>()</a>, <a href=
"../functions/nextafter.html"><i>nextafter</i>()</a>, <a href="../functions/pow.html"><i>pow</i>()</a>, <a href=
"../functions/remainder.html"><i>remainder</i>()</a>, <a href="../functions/rint.html"><i>rint</i>()</a>, <a href=
"../functions/scalb.html"><i>scalb</i>()</a>, <a href="../functions/sin.html"><i>sin</i>()</a>, <a href=
"../functions/sinh.html"><i>sinh</i>()</a>, <a href="../functions/sqrt.html"><i>sqrt</i>()</a>, <a href=
"../functions/tan.html"><i>tan</i>()</a>, <a href="../functions/tanh.html"><i>tanh</i>()</a>, <a href=
"../functions/y0.html"><i>y0</i>()</a></p>
</blockquote>
<h4><a name="tag_13_26_08"></a>CHANGE HISTORY</h4>
<blockquote>
<p>First released in Issue 1.</p>
</blockquote>
<h4><a name="tag_13_26_09"></a>Issue 6</h4>
<blockquote>
<p>This reference page is updated to align with the ISO/IEC&nbsp;9899:1999 standard.<br>
</p>
</blockquote>
<div class="box"><em>End of informative text.</em></div>
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