devdocs/c/numeric%2Ffenv%2Fferound.html


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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>
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