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| author | Craig Jennings <c@cjennings.net> | 2024-04-07 13:41:34 -0500 |
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| committer | Craig Jennings <c@cjennings.net> | 2024-04-07 13:41:34 -0500 |
| commit | 754bbf7a25a8dda49b5d08ef0d0443bbf5af0e36 (patch) | |
| tree | f1190704f78f04a2b0b4c977d20fe96a828377f1 /devdocs/c/numeric%2Ffenv%2Fferound.html | |
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diff --git a/devdocs/c/numeric%2Ffenv%2Fferound.html b/devdocs/c/numeric%2Ffenv%2Fferound.html new file mode 100644 index 00000000..7bbe06b4 --- /dev/null +++ b/devdocs/c/numeric%2Ffenv%2Fferound.html @@ -0,0 +1,88 @@ + <h1 id="firstHeading" class="firstHeading">fegetround, fesetround</h1> <table class="t-dcl-begin"> <tr class="t-dsc-header"> <th> Defined in header <code><fenv.h></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 <fenv.h> +#include <math.h> +#include <stdio.h> + +// #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 -> %+4.1f\n", rint(+11.5)); /* midway between two integers */ + printf("+12.5 -> %+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 -> %+4.1f\n", rint(+11.5)); + printf("+12.5 -> %+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 -> +12.0 ++12.5 -> +12.0 +current rounding direction: FE_DOWNWARD ++11.5 -> +11.0 ++12.5 -> +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"> + © 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> |
