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| <h3 class="section">4.5 Mapping of wide characters.</h3> |
| |
| <p>The classification functions are also generalized by the ISO C<!-- /@w --> |
| standard. Instead of just allowing the two standard mappings, a |
| locale can contain others. Again, the <code>localedef</code> program |
| already supports generating such locale data files. |
| |
| <!-- wctype.h --> |
| <!-- ISO --> |
| <div class="defun"> |
| — Data Type: <b>wctrans_t</b><var><a name="index-wctrans_005ft-446"></a></var><br> |
| <blockquote><p>This data type is defined as a scalar type which can hold a value |
| representing the locale-dependent character mapping. There is no way to |
| construct such a value apart from using the return value of the |
| <code>wctrans</code> function. |
| |
| <p><a name="index-wctype_002eh-447"></a>This type is defined in <samp><span class="file">wctype.h</span></samp>. |
| </p></blockquote></div> |
| |
| <!-- wctype.h --> |
| <!-- ISO --> |
| <div class="defun"> |
| — Function: wctrans_t <b>wctrans</b> (<var>const char *property</var>)<var><a name="index-wctrans-448"></a></var><br> |
| <blockquote><p>The <code>wctrans</code> function has to be used to find out whether a named |
| mapping is defined in the current locale selected for the |
| <code>LC_CTYPE</code> category. If the returned value is non-zero, you can use |
| it afterwards in calls to <code>towctrans</code>. If the return value is |
| zero no such mapping is known in the current locale. |
| |
| <p>Beside locale-specific mappings there are two mappings which are |
| guaranteed to be available in every locale: |
| |
| <p><table summary=""><tr align="left"><td valign="top" width="50%"><code>"tolower"</code> </td><td valign="top" width="50%"><code>"toupper"</code> |
| <br></td></tr></table> |
| |
| <p><a name="index-wctype_002eh-449"></a>These functions are declared in <samp><span class="file">wctype.h</span></samp>. |
| </p></blockquote></div> |
| |
| <!-- wctype.h --> |
| <!-- ISO --> |
| <div class="defun"> |
| — Function: wint_t <b>towctrans</b> (<var>wint_t wc, wctrans_t desc</var>)<var><a name="index-towctrans-450"></a></var><br> |
| <blockquote><p><code>towctrans</code> maps the input character <var>wc</var> |
| according to the rules of the mapping for which <var>desc</var> is a |
| descriptor, and returns the value it finds. <var>desc</var> must be |
| obtained by a successful call to <code>wctrans</code>. |
| |
| <p><a name="index-wctype_002eh-451"></a>This function is declared in <samp><span class="file">wctype.h</span></samp>. |
| </p></blockquote></div> |
| |
| <p>For the generally available mappings, the ISO C<!-- /@w --> standard defines |
| convenient shortcuts so that it is not necessary to call <code>wctrans</code> |
| for them. |
| |
| <!-- wctype.h --> |
| <!-- ISO --> |
| <div class="defun"> |
| — Function: wint_t <b>towlower</b> (<var>wint_t wc</var>)<var><a name="index-towlower-452"></a></var><br> |
| <blockquote><p>If <var>wc</var> is an upper-case letter, <code>towlower</code> returns the corresponding |
| lower-case letter. If <var>wc</var> is not an upper-case letter, |
| <var>wc</var> is returned unchanged. |
| |
| <p class="noindent"><code>towlower</code> can be implemented using |
| |
| <pre class="smallexample"> towctrans (wc, wctrans ("tolower")) |
| </pre> |
| <p><a name="index-wctype_002eh-453"></a>This function is declared in <samp><span class="file">wctype.h</span></samp>. |
| </p></blockquote></div> |
| |
| <!-- wctype.h --> |
| <!-- ISO --> |
| <div class="defun"> |
| — Function: wint_t <b>towupper</b> (<var>wint_t wc</var>)<var><a name="index-towupper-454"></a></var><br> |
| <blockquote><p>If <var>wc</var> is a lower-case letter, <code>towupper</code> returns the corresponding |
| upper-case letter. Otherwise <var>wc</var> is returned unchanged. |
| |
| <p class="noindent"><code>towupper</code> can be implemented using |
| |
| <pre class="smallexample"> towctrans (wc, wctrans ("toupper")) |
| </pre> |
| <p><a name="index-wctype_002eh-455"></a>This function is declared in <samp><span class="file">wctype.h</span></samp>. |
| </p></blockquote></div> |
| |
| <p>The same warnings given in the last section for the use of the wide |
| character classification functions apply here. It is not possible to |
| simply cast a <code>char</code> type value to a <code>wint_t</code> and use it as an |
| argument to <code>towctrans</code> calls. |
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