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| <h3 class="section">3.5 <code>isdigit</code>—decimal digit predicate</h3> |
| |
| <p><a name="index-isdigit-114"></a><strong>Synopsis</strong> |
| <pre class="example"> #include <ctype.h> |
| int isdigit(int <var>c</var>); |
| |
| </pre> |
| <p><strong>Description</strong><br> |
| <code>isdigit</code> is a macro which classifies ASCII integer values by table |
| lookup. It is a predicate returning non-zero for decimal digits, and 0 for |
| other characters. It is defined only if <var>c</var> is representable as an |
| unsigned char or if <var>c</var> is EOF. |
| |
| <p>You can use a compiled subroutine instead of the macro definition by |
| undefining the macro using `<code>#undef isdigit</code>'. |
| |
| <p><br> |
| <strong>Returns</strong><br> |
| <code>isdigit</code> returns non-zero if <var>c</var> is a decimal digit (<code>0</code>–<code>9</code>). |
| |
| <p><br> |
| <strong>Portability</strong><br> |
| <code>isdigit</code> is ANSI C. |
| |
| <p>No supporting OS subroutines are required. |
| |
| <p><br> |
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