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diff --git a/devdocs/c/numeric%2Fmath%2Flog.html b/devdocs/c/numeric%2Fmath%2Flog.html new file mode 100644 index 00000000..297dca2b --- /dev/null +++ b/devdocs/c/numeric%2Fmath%2Flog.html @@ -0,0 +1,84 @@ + <h1 id="firstHeading" class="firstHeading">log, logf, logl</h1> <table class="t-dcl-begin"> <tr class="t-dsc-header"> <th> Defined in header <code><math.h></code> </th> <th> </th> <th> </th> </tr> <tr class="t-dcl t-since-c99"> <td> <pre data-language="c">float logf( float arg );</pre> +</td> <td> (1) </td> <td> <span class="t-mark-rev t-since-c99">(since C99)</span> </td> </tr> <tr class="t-dcl"> <td> <pre data-language="c">double log( double arg );</pre> +</td> <td> (2) </td> <td class="t-dcl-nopad"> </td> </tr> <tr class="t-dcl t-since-c99"> <td> <pre data-language="c">long double logl( long double arg );</pre> +</td> <td> (3) </td> <td> <span class="t-mark-rev t-since-c99">(since C99)</span> </td> </tr> <tr class="t-dsc-header"> <th> Defined in header <code><tgmath.h></code> </th> <th> </th> <th> </th> </tr> <tr class="t-dcl t-since-c99"> <td> <pre data-language="c">#define log( arg )</pre> +</td> <td> (4) </td> <td> <span class="t-mark-rev t-since-c99">(since C99)</span> </td> </tr> </table> <div class="t-li1"> +<span class="t-li">1-3)</span> Computes the natural (base <i>e</i>) logarithm of <code>arg</code>.</div> <div class="t-li1"> +<span class="t-li">4)</span> Type-generic macro: If <code>arg</code> has type <code>long double</code>, <code>logl</code> is called. Otherwise, if <code>arg</code> has integer type or the type <code>double</code>, <code>log</code> is called. Otherwise, <code>logf</code> is called. If <code>arg</code> is complex or imaginary, then the macro invokes the corresponding complex function (<code><a href="http://en.cppreference.com/w/c/numeric/complex/clog"><span class="kw772">clogf</span></a></code>, <code><a href="http://en.cppreference.com/w/c/numeric/complex/clog"><span class="kw771">clog</span></a></code>, <code><a href="http://en.cppreference.com/w/c/numeric/complex/clog"><span class="kw773">clogl</span></a></code>).</div> <h3 id="Parameters"> Parameters</h3> <table class="t-par-begin"> <tr class="t-par"> <td> arg </td> <td> - </td> <td> floating point value </td> +</tr> +</table> <h3 id="Return_value"> Return value</h3> <p>If no errors occur, the natural (base-<i>e</i>) logarithm of <code>arg</code> (ln(arg) or log<sub class="t-su t-su-b">e</sub>(arg)) is returned.</p> +<p>If a domain error occurs, an implementation-defined value is returned (NaN where supported).</p> +<p>If a pole error occurs, <code><a href="huge_val" title="c/numeric/math/HUGE VAL">-HUGE_VAL</a></code>, <code>-HUGE_VALF</code>, or <code>-HUGE_VALL</code> is returned.</p> +<h3 id="Error_handling"> Error handling</h3> <p>Errors are reported as specified in <a href="math_errhandling" title="c/numeric/math/math errhandling"><code>math_errhandling</code></a>.</p> +<p>Domain error occurs if <code>arg</code> is less than zero.</p> +<p>Pole error may occur if <code>arg</code> is zero.</p> +<p>If the implementation supports IEEE floating-point arithmetic (IEC 60559),</p> +<ul> +<li> If the argument is ±0, -∞ is returned and <code><a href="../fenv/fe_exceptions" title="c/numeric/fenv/FE exceptions">FE_DIVBYZERO</a></code> is raised. </li> +<li> If the argument is 1, +0 is returned </li> +<li> If the argument is negative, NaN is returned and <code><a href="../fenv/fe_exceptions" title="c/numeric/fenv/FE exceptions">FE_INVALID</a></code> is raised. </li> +<li> If the argument is +∞, +∞ is returned </li> +<li> If the argument is NaN, NaN is returned </li> +</ul> <h3 id="Example"> Example</h3> <div class="t-example"> <div class="c source-c"><pre data-language="c">#include <stdio.h> +#include <math.h> +#include <float.h> +#include <errno.h> +#include <fenv.h> +// #pragma STDC FENV_ACCESS ON +int main(void) +{ + printf("log(1) = %f\n", log(1)); + printf("base-5 logarithm of 125 = %f\n", log(125)/log(5)); + // special values + printf("log(1) = %f\n", log(1)); + printf("log(+Inf) = %f\n", log(INFINITY)); + //error handling + errno = 0; feclearexcept(FE_ALL_EXCEPT); + printf("log(0) = %f\n", log(0)); + if(errno == ERANGE) perror(" errno == ERANGE"); + if(fetestexcept(FE_DIVBYZERO)) puts(" FE_DIVBYZERO raised"); +}</pre></div> <p>Output:</p> +<div class="text source-text"><pre data-language="c">log(1) = 0.000000 +base-5 logarithm of 125 = 3.000000 +log(1) = 0.000000 +log(+Inf) = inf +log(0) = -inf + errno == ERANGE: Numerical result out of range + FE_DIVBYZERO raised</pre></div> </div> <h3 id="References"> References</h3> <ul> +<li> C17 standard (ISO/IEC 9899:2018): </li> +<ul> +<li> 7.12.6.7 The log functions (p: 178-179) </li> +<li> 7.25 Type-generic math <tgmath.h> (p: 272-273) </li> +<li> F.10.3.7 The log functions (p: 380) </li> +</ul> +<li> C11 standard (ISO/IEC 9899:2011): </li> +<ul> +<li> 7.12.6.7 The log functions (p: 244-245) </li> +<li> 7.25 Type-generic math <tgmath.h> (p: 373-375) </li> +<li> F.10.3.7 The log functions (p: 522) </li> +</ul> +<li> C99 standard (ISO/IEC 9899:1999): </li> +<ul> +<li> 7.12.6.7 The log functions (p: 225) </li> +<li> 7.22 Type-generic math <tgmath.h> (p: 335-337) </li> +<li> F.9.3.7 The log functions (p: 459) </li> +</ul> +<li> C89/C90 standard (ISO/IEC 9899:1990): </li> +<ul><li> 4.5.4.4 The log function </li></ul> +</ul> <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <tr class="t-dsc"> <td> <div><a href="log10" title="c/numeric/math/log10"> <span class="t-lines"><span>log10</span><span>log10f</span><span>log10l</span></span></a></div> +<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> computes common (base-<i>10</i>) logarithm (\({\small \log_{10}{x} }\)log<sub>10</sub>(x)) <br> <span class="t-mark">(function)</span> </td> +</tr> <tr class="t-dsc"> <td> <div><a href="log2" title="c/numeric/math/log2"> <span class="t-lines"><span>log2</span><span>log2f</span><span>log2l</span></span></a></div> +<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> computes base-2 logarithm (\({\small \log_{2}{x} }\)log<sub>2</sub>(x)) <br> <span class="t-mark">(function)</span> </td> +</tr> <tr class="t-dsc"> <td> <div><a href="log1p" title="c/numeric/math/log1p"> <span class="t-lines"><span>log1p</span><span>log1pf</span><span>log1pl</span></span></a></div> +<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> computes natural (base-<i>e</i>) logarithm of 1 plus the given number (\({\small \ln{(1+x)} }\)ln(1+x)) <br> <span class="t-mark">(function)</span> </td> +</tr> <tr class="t-dsc"> <td> <div><a href="exp" title="c/numeric/math/exp"> <span class="t-lines"><span>exp</span><span>expf</span><span>expl</span></span></a></div> +<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> computes <i>e</i> raised to the given power (\({\small e^x}\)e<sup>x</sup>) <br> <span class="t-mark">(function)</span> </td> +</tr> <tr class="t-dsc"> <td> <div><a href="../complex/clog" title="c/numeric/complex/clog"> <span class="t-lines"><span>clog</span><span>clogf</span><span>clogl</span></span></a></div> +<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> computes the complex natural logarithm <br> <span class="t-mark">(function)</span> </td> +</tr> <tr class="t-dsc"> <td colspan="2"> <span><a href="https://en.cppreference.com/w/cpp/numeric/math/log" title="cpp/numeric/math/log">C++ documentation</a></span> for <code>log</code> </td> +</tr> </table> <div class="_attribution"> + <p class="_attribution-p"> + © cppreference.com<br>Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.<br> + <a href="https://en.cppreference.com/w/c/numeric/math/log" class="_attribution-link">https://en.cppreference.com/w/c/numeric/math/log</a> + </p> +</div> |