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diff --git a/devdocs/c/string%2Fbyte%2Fatof.html b/devdocs/c/string%2Fbyte%2Fatof.html new file mode 100644 index 00000000..54760677 --- /dev/null +++ b/devdocs/c/string%2Fbyte%2Fatof.html @@ -0,0 +1,73 @@ + <h1 id="firstHeading" class="firstHeading">atof</h1> <table class="t-dcl-begin"> <tr class="t-dsc-header"> <th> Defined in header <code><stdlib.h></code> </th> <th> </th> <th> </th> </tr> <tr class="t-dcl"> <td class="t-dcl-nopad"> <pre data-language="c">double atof( const char* str );</pre> +</td> <td class="t-dcl-nopad"> </td> <td class="t-dcl-nopad"> </td> </tr> </table> <p>Interprets a floating-point value in a byte string pointed to by <code>str</code>.</p> +<p>Function discards any whitespace characters (as determined by <code><a href="isspace" title="c/string/byte/isspace">isspace</a></code>) until first non-whitespace character is found. Then it takes as many characters as possible to form a valid floating-point representation and converts them to a floating-point value. The valid floating-point value can be one of the following:</p> +<ul> +<li>decimal floating-point expression. It consists of the following parts: </li> +<ul> +<li> <span class="t-mark">(optional)</span> plus or minus sign </li> +<li> nonempty sequence of decimal digits optionally containing decimal-point character (as determined by the current C <a href="../../locale/setlocale" title="c/locale/setlocale">locale</a>) (defines significand) </li> +<li> <span class="t-mark">(optional)</span> <code>e</code> or <code>E</code> followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent to base 10) </li> +</ul> +</ul> <table class="t-rev-begin"> <tr class="t-rev t-since-c99"> +<td> <ul> +<li>hexadecimal floating-point expression. It consists of the following parts: </li> +<ul> +<li> <span class="t-mark">(optional)</span> plus or minus sign </li> +<li> <code>0x</code> or <code>0X</code> </li> +<li> nonempty sequence of hexadecimal digits optionally containing a decimal-point character (as determined by the current C <a href="../../locale/setlocale" title="c/locale/setlocale">locale</a>) (defines significand) </li> +<li> <span class="t-mark">(optional)</span> <code>p</code> or <code>P</code> followed with optional minus or plus sign and nonempty sequence of decimal digits (defines exponent to base 2) </li> +</ul> +<li> infinity expression. It consists of the following parts: </li> +<ul> +<li> <span class="t-mark">(optional)</span> plus or minus sign </li> +<li> <code>INF</code> or <code>INFINITY</code> ignoring case </li> +</ul> +<li> not-a-number expression. It consists of the following parts: </li> +<ul> +<li> <span class="t-mark">(optional)</span> plus or minus sign </li> +<li> <code>NAN</code> or <code>NAN(</code><i>char_sequence</i><code>)</code> ignoring case of the <code>NAN</code> part. <i>char_sequence</i> can only contain digits, Latin letters, and underscores. The result is a quiet NaN floating-point value. </li> +</ul> +</ul> </td> <td><span class="t-mark-rev t-since-c99">(since C99)</span></td> +</tr> </table> <ul><li> any other expression that may be accepted by the currently installed C <a href="../../locale/setlocale" title="c/locale/setlocale">locale</a> </li></ul> <h3 id="Parameters"> Parameters</h3> <table class="t-par-begin"> <tr class="t-par"> <td> str </td> <td> - </td> <td> pointer to the null-terminated byte string to be interpreted </td> +</tr> +</table> <h3 id="Return_value"> Return value</h3> <p><code>double</code> value corresponding to the contents of <code>str</code> on success. If the converted value falls out of range of the return type, the return value is undefined. If no conversion can be performed, <code>0.0</code> is returned.</p> +<h3 id="Notes"> Notes</h3> <p>The name stands for "ASCII to float".</p> +<h3 id="Example"> Example</h3> <div class="t-example"> <div class="c source-c"><pre data-language="c">#include <stdlib.h> +#include <stdio.h> + +int main(void) +{ + printf("%g\n", atof(" -0.0000000123junk")); + printf("%g\n", atof("0.012")); + printf("%g\n", atof("15e16")); + printf("%g\n", atof("-0x1afp-2")); + printf("%g\n", atof("inF")); + printf("%g\n", atof("Nan")); + printf("%g\n", atof("1.0e+309")); // UB: out of range of double + printf("%g\n", atof("0.0")); + printf("%g\n", atof("junk")); // no conversion can be performed +}</pre></div> <p>Possible output:</p> +<div class="text source-text"><pre data-language="c">-1.23e-08 +0.012 +1.5e+17 +-107.75 +inf +nan +inf +0 +0</pre></div> </div> <h3 id="References"> References</h3> <ul> +<li> C11 standard (ISO/IEC 9899:2011): </li> +<ul><li> 7.22.1.1 The atof function (p: 341) </li></ul> +<li> C99 standard (ISO/IEC 9899:1999): </li> +<ul><li> 7.20.1.1 The atof function (p: 307) </li></ul> +<li> C89/C90 standard (ISO/IEC 9899:1990): </li> +<ul><li> 4.10.1.1 The atof function </li></ul> +</ul> <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <tr class="t-dsc"> <td> <div><a href="strtof" title="c/string/byte/strtof"> <span class="t-lines"><span>strtof</span><span>strtod</span><span>strtold</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> converts a byte string to a floating point value <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/string/byte/atof" title="cpp/string/byte/atof">C++ documentation</a></span> for <code>atof</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/string/byte/atof" class="_attribution-link">https://en.cppreference.com/w/c/string/byte/atof</a> + </p> +</div> |