1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
|
<h1 id="firstHeading" class="firstHeading">fpclassify</h1> <table class="t-dcl-begin"> <tr class="t-dsc-header"> <th> Defined in header <code><math.h></code> </th> <th> </th> <th> </th> </tr> <tr class="t-dcl t-since-c99"> <td> <pre data-language="c">#define fpclassify(arg) /* implementation defined */</pre>
</td> <td class="t-dcl-nopad"> </td> <td> <span class="t-mark-rev t-since-c99">(since C99)</span> </td> </tr> </table> <p>Categorizes floating point value <code>arg</code> into the following categories: zero, subnormal, normal, infinite, NAN, or implementation-defined category. The macro returns an integral value.</p>
<p><code><a href="../../types/limits/flt_eval_method" title="c/types/limits/FLT EVAL METHOD">FLT_EVAL_METHOD</a></code> is ignored: even if the argument is evaluated with more range and precision than its type, it is first converted to its semantic type, and the classification is based on that: a normal long double value might become subnormal when converted to double and zero when converted to float.</p>
<h3 id="Parameters"> Parameters</h3> <table class="t-par-begin"> <tr class="t-par"> <td> arg </td> <td> - </td> <td> floating point value </td>
</tr>
</table> <h3 id="Return_value"> Return value</h3> <p>One of <code><a href="fp_categories" title="c/numeric/math/FP categories">FP_INFINITE</a></code>, <code><a href="fp_categories" title="c/numeric/math/FP categories">FP_NAN</a></code>, <code><a href="fp_categories" title="c/numeric/math/FP categories">FP_NORMAL</a></code>, <code><a href="fp_categories" title="c/numeric/math/FP categories">FP_SUBNORMAL</a></code>, <code><a href="fp_categories" title="c/numeric/math/FP categories">FP_ZERO</a></code> or implementation-defined type, specifying the category of <code>arg</code>.</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 <float.h>
const char *show_classification(double x) {
switch(fpclassify(x)) {
case FP_INFINITE: return "Inf";
case FP_NAN: return "NaN";
case FP_NORMAL: return "normal";
case FP_SUBNORMAL: return "subnormal";
case FP_ZERO: return "zero";
default: return "unknown";
}
}
int main(void)
{
printf("1.0/0.0 is %s\n", show_classification(1/0.0));
printf("0.0/0.0 is %s\n", show_classification(0.0/0.0));
printf("DBL_MIN/2 is %s\n", show_classification(DBL_MIN/2));
printf("-0.0 is %s\n", show_classification(-0.0));
printf("1.0 is %s\n", show_classification(1.0));
}</pre></div> <p>Output:</p>
<div class="text source-text"><pre data-language="c">1.0/0.0 is Inf
0.0/0.0 is NaN
DBL_MIN/2 is subnormal
-0.0 is zero
1.0 is normal</pre></div> </div> <h3 id="References"> References</h3> <ul>
<li> C11 standard (ISO/IEC 9899:2011): </li>
<ul><li> 7.12.3.1 The fpclassify macro (p: 235) </li></ul>
<li> C99 standard (ISO/IEC 9899:1999): </li>
<ul><li> 7.12.3.1 The fpclassify macro (p: 216) </li></ul>
</ul> <h3 id="See_also"> See also</h3> <table class="t-dsc-begin"> <tr class="t-dsc"> <td> <div><a href="isfinite" title="c/numeric/math/isfinite"> <span class="t-lines"><span>isfinite</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> checks if the given number has finite value <br> <span class="t-mark">(function macro)</span> </td>
</tr> <tr class="t-dsc"> <td> <div><a href="isinf" title="c/numeric/math/isinf"> <span class="t-lines"><span>isinf</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> checks if the given number is infinite <br> <span class="t-mark">(function macro)</span> </td>
</tr> <tr class="t-dsc"> <td> <div><a href="isnan" title="c/numeric/math/isnan"> <span class="t-lines"><span>isnan</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> checks if the given number is NaN <br> <span class="t-mark">(function macro)</span> </td>
</tr> <tr class="t-dsc"> <td> <div><a href="isnormal" title="c/numeric/math/isnormal"> <span class="t-lines"><span>isnormal</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> checks if the given number is normal <br> <span class="t-mark">(function macro)</span> </td>
</tr> <tr class="t-dsc"> <td colspan="2"> <span><a href="https://en.cppreference.com/w/cpp/numeric/math/fpclassify" title="cpp/numeric/math/fpclassify">C++ documentation</a></span> for <code>fpclassify</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/math/fpclassify" class="_attribution-link">https://en.cppreference.com/w/c/numeric/math/fpclassify</a>
</p>
</div>
|
