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authorCraig Jennings <c@cjennings.net>2024-04-07 13:41:34 -0500
committerCraig Jennings <c@cjennings.net>2024-04-07 13:41:34 -0500
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+ <h1 id="firstHeading" class="firstHeading">fegetround, fesetround</h1> <table class="t-dcl-begin"> <tr class="t-dsc-header"> <th> Defined in header <code>&lt;fenv.h&gt;</code> </th> <th> </th> <th> </th> </tr> <tr class="t-dcl t-since-c99"> <td> <pre data-language="c">int fesetround( int round );</pre>
+</td> <td> (1) </td> <td> <span class="t-mark-rev t-since-c99">(since C99)</span> </td> </tr> <tr class="t-dcl t-since-c99"> <td> <pre data-language="c">int fegetround();</pre>
+</td> <td> (2) </td> <td> <span class="t-mark-rev t-since-c99">(since C99)</span> </td> </tr> </table> <p>1) Attempts to establish the floating-point rounding direction equal to the argument <code>round</code>, which is expected to be one of the <a href="fe_round" title="c/numeric/fenv/FE round">floating-point rounding macros</a>.</p>
+<p>2) Returns the value of the <a href="fe_round" title="c/numeric/fenv/FE round">floating-point rounding macro</a> that corresponds to the current rounding direction.</p>
+<h3 id="Parameters"> Parameters</h3> <table class="t-par-begin"> <tr class="t-par"> <td> round </td> <td> - </td> <td> rounding direction, one of <a href="fe_round" title="c/numeric/fenv/FE round">floating-point rounding macros</a> </td>
+</tr>
+</table> <h3 id="Return_value"> Return value</h3> <p>1) <code>​0​</code> on success, non-zero otherwise.</p>
+<p>2) the <a href="fe_round" title="c/numeric/fenv/FE round">floating-point rounding macro</a> describing the current rounding direction or a negative value if the direction cannot be determined.</p>
+<h3 id="Notes"> Notes</h3> <p>The current rounding mode, reflecting the effects of the most recent <code>fesetround</code>, can also be queried with <code><a href="../../types/limits/flt_rounds" title="c/types/limits/FLT ROUNDS">FLT_ROUNDS</a></code>.</p>
+<h3 id="Example"> Example</h3> <div class="t-example"> <div class="c source-c"><pre data-language="c">#include &lt;fenv.h&gt;
+#include &lt;math.h&gt;
+#include &lt;stdio.h&gt;
+
+// #pragma STDC FENV_ACCESS ON
+
+void show_fe_current_rounding_direction(void)
+{
+ printf("current rounding direction: ");
+ switch (fegetround()) {
+ case FE_TONEAREST: printf ("FE_TONEAREST"); break;
+ case FE_DOWNWARD: printf ("FE_DOWNWARD"); break;
+ case FE_UPWARD: printf ("FE_UPWARD"); break;
+ case FE_TOWARDZERO: printf ("FE_TOWARDZERO"); break;
+ default: printf ("unknown");
+ };
+ printf("\n");
+}
+
+int main(void)
+{
+ /* Default rounding direction */
+ show_fe_current_rounding_direction();
+ printf("+11.5 -&gt; %+4.1f\n", rint(+11.5)); /* midway between two integers */
+ printf("+12.5 -&gt; %+4.1f\n", rint(+12.5)); /* midway between two integers */
+
+ /* Save current rounding direction. */
+ int curr_direction = fegetround();
+
+ /* Temporarily change current rounding direction. */
+ fesetround(FE_DOWNWARD);
+ show_fe_current_rounding_direction();
+ printf("+11.5 -&gt; %+4.1f\n", rint(+11.5));
+ printf("+12.5 -&gt; %+4.1f\n", rint(+12.5));
+
+ /* Restore default rounding direction. */
+ fesetround(curr_direction);
+ show_fe_current_rounding_direction();
+
+ return 0;
+}</pre></div> <p>Possible output:</p>
+<div class="text source-text"><pre data-language="c">current rounding direction: FE_TONEAREST
++11.5 -&gt; +12.0
++12.5 -&gt; +12.0
+current rounding direction: FE_DOWNWARD
++11.5 -&gt; +11.0
++12.5 -&gt; +12.0
+current rounding direction: FE_TONEAREST</pre></div> </div> <h3 id="References"> References</h3> <ul>
+<li> C23 standard (ISO/IEC 9899:2023): </li>
+<ul>
+<li> 7.6.3.1 The fegetround function (p: TBD) </li>
+<li> 7.6.3.2 The fesetround function (p: TBD) </li>
+</ul>
+<li> C17 standard (ISO/IEC 9899:2018): </li>
+<ul>
+<li> 7.6.3.1 The fegetround function (p: TBD) </li>
+<li> 7.6.3.2 The fesetround function (p: TBD) </li>
+</ul>
+<li> C11 standard (ISO/IEC 9899:2011): </li>
+<ul>
+<li> 7.6.3.1 The fegetround function (p: 212) </li>
+<li> 7.6.3.2 The fesetround function (p: 212-213) </li>
+</ul>
+<li> C99 standard (ISO/IEC 9899:1999): </li>
+<ul>
+<li> 7.6.3.1 The fegetround function (p: 193) </li>
+<li> 7.6.3.2 The fesetround function (p: 193-194) </li>
+</ul>
+</ul> <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <tr class="t-dsc"> <td> <div><a href="../math/nearbyint" title="c/numeric/math/nearbyint"> <span class="t-lines"><span>nearbyint</span><span>nearbyintf</span><span>nearbyintl</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> rounds to an integer using current rounding mode <br> <span class="t-mark">(function)</span> </td>
+</tr> <tr class="t-dsc"> <td> <div><a href="../math/rint" title="c/numeric/math/rint"> <span class="t-lines"><span>rint</span><span>rintf</span><span>rintl</span><span>lrint</span><span>lrintf</span><span>lrintl</span><span>llrint</span><span>llrintf</span><span>llrintl</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><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><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> rounds to an integer using current rounding mode with <br> exception if the result differs <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/fenv/feround" title="cpp/numeric/fenv/feround">C++ documentation</a></span> for <code>fegetround, fesetround</code> </td>
+</tr> </table> <div class="_attribution">
+ <p class="_attribution-p">
+ &copy; cppreference.com<br>Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.<br>
+ <a href="https://en.cppreference.com/w/c/numeric/fenv/feround" class="_attribution-link">https://en.cppreference.com/w/c/numeric/fenv/feround</a>
+ </p>
+</div>