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| <h3 class="section">4.2 Case Conversion</h3> |
| |
| <p><a name="index-character-case-conversion-396"></a><a name="index-case-conversion-of-characters-397"></a><a name="index-converting-case-of-characters-398"></a> |
| This section explains the library functions for performing conversions |
| such as case mappings on characters. For example, <code>toupper</code> |
| converts any character to upper case if possible. If the character |
| can't be converted, <code>toupper</code> returns it unchanged. |
| |
| <p>These functions take one argument of type <code>int</code>, which is the |
| character to convert, and return the converted character as an |
| <code>int</code>. If the conversion is not applicable to the argument given, |
| the argument is returned unchanged. |
| |
| <p><strong>Compatibility Note:</strong> In pre-ISO C<!-- /@w --> dialects, instead of |
| returning the argument unchanged, these functions may fail when the |
| argument is not suitable for the conversion. Thus for portability, you |
| may need to write <code>islower(c) ? toupper(c) : c</code> rather than just |
| <code>toupper(c)</code>. |
| |
| <p>These functions are declared in the header file <samp><span class="file">ctype.h</span></samp>. |
| <a name="index-ctype_002eh-399"></a> |
| <!-- ctype.h --> |
| <!-- ISO --> |
| |
| <div class="defun"> |
| — Function: int <b>tolower</b> (<var>int c</var>)<var><a name="index-tolower-400"></a></var><br> |
| <blockquote><p>If <var>c</var> is an upper-case letter, <code>tolower</code> returns the corresponding |
| lower-case letter. If <var>c</var> is not an upper-case letter, |
| <var>c</var> is returned unchanged. |
| </p></blockquote></div> |
| |
| <!-- ctype.h --> |
| <!-- ISO --> |
| <div class="defun"> |
| — Function: int <b>toupper</b> (<var>int c</var>)<var><a name="index-toupper-401"></a></var><br> |
| <blockquote><p>If <var>c</var> is a lower-case letter, <code>toupper</code> returns the corresponding |
| upper-case letter. Otherwise <var>c</var> is returned unchanged. |
| </p></blockquote></div> |
| |
| <!-- ctype.h --> |
| <!-- SVID, BSD --> |
| <div class="defun"> |
| — Function: int <b>toascii</b> (<var>int c</var>)<var><a name="index-toascii-402"></a></var><br> |
| <blockquote><p>This function converts <var>c</var> to a 7-bit <code>unsigned char</code> value |
| that fits into the US/UK ASCII character set, by clearing the high-order |
| bits. This function is a BSD extension and is also an SVID extension. |
| </p></blockquote></div> |
| |
| <!-- ctype.h --> |
| <!-- SVID --> |
| <div class="defun"> |
| — Function: int <b>_tolower</b> (<var>int c</var>)<var><a name="index-g_t_005ftolower-403"></a></var><br> |
| <blockquote><p>This is identical to <code>tolower</code>, and is provided for compatibility |
| with the SVID. See <a href="SVID.html#SVID">SVID</a>. |
| </p></blockquote></div> |
| |
| <!-- ctype.h --> |
| <!-- SVID --> |
| <div class="defun"> |
| — Function: int <b>_toupper</b> (<var>int c</var>)<var><a name="index-g_t_005ftoupper-404"></a></var><br> |
| <blockquote><p>This is identical to <code>toupper</code>, and is provided for compatibility |
| with the SVID. |
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