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diff --git a/devdocs/c/numeric%2Ffenv%2Ffeenv.html b/devdocs/c/numeric%2Ffenv%2Ffeenv.html new file mode 100644 index 00000000..55c9bb86 --- /dev/null +++ b/devdocs/c/numeric%2Ffenv%2Ffeenv.html @@ -0,0 +1,116 @@ + <h1 id="firstHeading" class="firstHeading">fegetenv, fesetenv</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 fegetenv( fenv_t* envp );</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 fesetenv( const fenv_t* envp );</pre> +</td> <td> (2) </td> <td> <span class="t-mark-rev t-since-c99">(since C99)</span> </td> </tr> </table> <p>1) Attempts to store the status of the floating-point environment in the object pointed to by <code>envp</code>.</p> +<p>2) Attempts to establish the floating-point environment from the object pointed to by <code>envp</code>. The value of that object must be previously obtained by a call to <code><a href="feholdexcept" title="c/numeric/fenv/feholdexcept">feholdexcept</a></code> or <code>fegetenv</code> or be a floating-point macro constant. If any of the floating-point status flags are set in <code>envp</code>, they become set in the environment (and are then testable with <code><a href="fetestexcept" title="c/numeric/fenv/fetestexcept">fetestexcept</a></code>), but the corresponding floating-point exceptions are not raised (execution continues uninterrupted)</p> +<h3 id="Parameters"> Parameters</h3> <table class="t-par-begin"> <tr class="t-par"> <td> envp </td> <td> - </td> <td> pointer to the object of type <code>fenv_t</code> which holds the status of the floating-point environment </td> +</tr> +</table> <h3 id="Return_value"> Return value</h3> <p><code>0</code> on success, non-zero otherwise.</p> +<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 <fenv.h> + +#pragma STDC FENV_ACCESS ON + +void show_fe_exceptions(void) +{ + printf("current exceptions raised: "); + if(fetestexcept(FE_DIVBYZERO)) printf(" FE_DIVBYZERO"); + if(fetestexcept(FE_INEXACT)) printf(" FE_INEXACT"); + if(fetestexcept(FE_INVALID)) printf(" FE_INVALID"); + if(fetestexcept(FE_OVERFLOW)) printf(" FE_OVERFLOW"); + if(fetestexcept(FE_UNDERFLOW)) printf(" FE_UNDERFLOW"); + if(fetestexcept(FE_ALL_EXCEPT)==0) printf(" none"); + printf("\n"); +} + +void show_fe_rounding_method(void) +{ + printf("current rounding method: "); + 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"); +} + +void show_fe_environment(void) +{ + show_fe_exceptions(); + show_fe_rounding_method(); +} + +int main(void) +{ + fenv_t curr_env; + int rtn; + + /* Show default environment. */ + show_fe_environment(); + printf("\n"); + + /* Perform some computation under default environment. */ + 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 */ + show_fe_environment(); + printf("\n"); + + /* Save current environment. */ + rtn = fegetenv(&curr_env); + + /* Perform some computation with new rounding method. */ + feclearexcept(FE_ALL_EXCEPT); + fesetround(FE_DOWNWARD); + printf("1.0/0.0 = %f\n", 1.0/0.0); + printf("+11.5 -> %+4.1f\n", rint(+11.5)); + printf("+12.5 -> %+4.1f\n", rint(+12.5)); + show_fe_environment(); + printf("\n"); + + /* Restore previous environment. */ + rtn = fesetenv(&curr_env); + show_fe_environment(); + + return 0; +}</pre></div> <p>Output:</p> +<div class="text source-text"><pre data-language="c">current exceptions raised: none +current rounding method: FE_TONEAREST + ++11.5 -> +12.0 ++12.5 -> +12.0 +current exceptions raised: FE_INEXACT +current rounding method: FE_TONEAREST + +1.0/0.0 = inf ++11.5 -> +11.0 ++12.5 -> +12.0 +current exceptions raised: FE_DIVBYZERO FE_INEXACT +current rounding method: FE_DOWNWARD + +current exceptions raised: FE_INEXACT +current rounding method: FE_TONEAREST</pre></div> </div> <h3 id="References"> References</h3> <ul> +<li> C11 standard (ISO/IEC 9899:2011): </li> +<ul> +<li> 7.6.4.1 The fegetenv function (p: 213) </li> +<li> 7.6.4.3 The fesetenv function (p: 214) </li> +</ul> +<li> C99 standard (ISO/IEC 9899:1999): </li> +<ul> +<li> 7.6.4.1 The fegetenv function (p: 194) </li> +<li> 7.6.4.3 The fesetenv function (p: 195) </li> +</ul> +</ul> <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <tr class="t-dsc"> <td> <div><a href="feholdexcept" title="c/numeric/fenv/feholdexcept"> <span class="t-lines"><span>feholdexcept</span></span></a></div> +<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> saves the environment, clears all status flags and ignores all future errors <br> <span class="t-mark">(function)</span> </td> +</tr> <tr class="t-dsc"> <td> <div><a href="feupdateenv" title="c/numeric/fenv/feupdateenv"> <span class="t-lines"><span>feupdateenv</span></span></a></div> +<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> restores the floating-point environment and raises the previously raise exceptions <br> <span class="t-mark">(function)</span> </td> +</tr> <tr class="t-dsc"> <td> <div><a href="fe_dfl_env" title="c/numeric/fenv/FE DFL ENV"> <span class="t-lines"><span>FE_DFL_ENV</span></span></a></div> +<div><span class="t-lines"><span><span class="t-mark-rev t-since-c99">(C99)</span></span></span></div> </td> <td> default floating-point environment <br> <span class="t-mark">(macro constant)</span> </td> +</tr> <tr class="t-dsc"> <td colspan="2"> <span><a href="https://en.cppreference.com/w/cpp/numeric/fenv/feenv" title="cpp/numeric/fenv/feenv">C++ documentation</a></span> for <code>fegetenv, fesetenv</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/feenv" class="_attribution-link">https://en.cppreference.com/w/c/numeric/fenv/feenv</a> + </p> +</div> |