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<html><title>Programming Ruby: The Pragmatic Programmer's Guide</title><head><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><STYLE TYPE="text/css"><!--
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</STYLE><table bgcolor="#a03030" cellpadding="3" border="0" cellspacing="0"><tr><td colspan="3"><table bgcolor="#902020" cellpadding="20"><tr><td><h1 class="header">Programming Ruby</h1><h3 class="subheader">The Pragmatic Programmer's Guide</h3></td></tr></table></td></tr><tr><td width="33%" align="left"><a class="subheader" href="ref_c_trueclass.html">Previous <</a></td><td width="33%" align="center" valign="middle"><a class="subheader" href="builtins.html">Contents ^</a><br></td><td width="33%" align="right"><a class="subheader" href="ref_m_enumerable.html">Next ></a><br></td></tr></table></head><body bgcolor="white">
<!--
Copyright (c) 2001 by Addison Wesley Longman. This
material may be distributed only subject to the terms and
conditions set forth in the Open Publication License, v1.0 or
later (the latest version is presently available at
http://www.opencontent.org/openpub/).
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<table><tr><td height="20"><img src="dot.gif" width="1" height="20"></td></tr></table><table border="0" width="100%" bgcolor="660066" cellpadding="10"><tr><td valign="center"><font color="white" size="7">module Comparable</font></td><td><table border="0"><tr><td><font color="white">
Relies on:
</font></td><td><font color="white"><=></font></td></tr></table></td></tr></table><p></p><H3>Index:</H3><a href="#Comparisons"><i>Comparisons</i></a> <a href="#between_qm"><i>between?</i></a> <p></p><hr>
<P></P>
The <code>Comparable</code> mixin is used by classes whose objects may be
ordered. The class must define the <code><=></code>
operator, which
compares the receiver against another object, returning -1, 0,
or +1 depending on whether the receiver is less than, equal to, or
greater than the other object. <code>Comparable</code> uses <code><=></code> to implement the
conventional comparison operators (<code><</code>, <code><=</code>, <code>==</code>,
<code>>=</code>, and <code>></code>) and the method <code>between?</code>.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td colspan="3" valign="top"><code>class SizeMatters</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code> include Comparable</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code> attr :str</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code> def <=>(anOther)</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code> str.size <=> anOther.str.size</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code> end</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code> def initialize(str)</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code> @str = str</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code> end</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code> def inspect</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code> @str</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code> end</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>end</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code></code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>s1 = SizeMatters.new("Z")</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>s2 = SizeMatters.new("YY")</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>s3 = SizeMatters.new("XXX")</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>s4 = SizeMatters.new("WWWW")</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code>s5 = SizeMatters.new("VVVVV")</code></td>
</tr>
<tr>
<td colspan="3" valign="top"><code></code></td>
</tr>
<tr>
<td valign="top"><code>s1 < s2</code></td>
<td valign="top"></td>
<td valign="top"><code>true</code></td>
</tr>
<tr>
<td valign="top"><code>s4.between?(s1, s3)</code></td>
<td valign="top"></td>
<td valign="top"><code>false</code></td>
</tr>
<tr>
<td valign="top"><code>s4.between?(s3, s5)</code></td>
<td valign="top"></td>
<td valign="top"><code>true</code></td>
</tr>
<tr>
<td valign="top"><code>[ s3, s2, s5, s4, s1 ].sort</code></td>
<td valign="top"></td>
<td valign="top"><code>[Z, YY, XXX, WWWW, VVVVV]</code></td>
</tr>
</table>
<P></P>
<P></P>
<table border="0" width="100%" cellpadding="10"><tr><td valign="center" colspan="2" bgcolor="990066"><font color="white" size="6">instance methods
</font></td></tr><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="Comparisons"><b>Comparisons</b></a></font></td><td bgcolor="#ffaaaa">
<i>anObject</i> < <i>otherObject</i> -> <code>true</code> or <code>false</code><br><i>anObject</i> <= <i>otherObject</i> -> <code>true</code> or <code>false</code><br><i>anObject</i> == <i>otherObject</i> -> <code>true</code> or <code>false</code><br><i>anObject</i> >= <i>otherObject</i> -> <code>true</code> or <code>false</code><br><i>anObject</i> > <i>otherObject</i> -> <code>true</code> or <code>false</code><br>
</td></tr><td></td><td>
<P></P>
Compares two objects based on the receiver's <code><=></code> method.
<P></P>
</td><tr><td valign="center" bgcolor="#ff9999"><font size="4"><a name="between_qm"><b>between?</b></a></font></td><td bgcolor="#ffaaaa">
<i>anObject</i>.between?( <i>min</i>, <i>max</i> )
-> <code>true</code> or <code>false</code>
</td></tr><td></td><td>
<P></P>
Returns <code>false</code> if <i>anObject</i> <code><=></code> <i>min</i> is less than
zero or if <i>anObject</i> <code><=></code> <i>max</i> is greater than zero,
<code>true</code> otherwise.
<P></P>
<table bgcolor="#fff0f0" cellspacing="0" border="0" cellpadding="3" width="500">
<tr>
<td valign="top"><code>3.between?(1, 5)</code></td>
<td valign="top"></td>
<td valign="top"><code>true</code></td>
</tr>
<tr>
<td valign="top"><code>6.between?(1, 5)</code></td>
<td valign="top"></td>
<td valign="top"><code>false</code></td>
</tr>
<tr>
<td valign="top"><code>'cat'.between?('ant', 'dog')</code></td>
<td valign="top"></td>
<td valign="top"><code>true</code></td>
</tr>
<tr>
<td valign="top"><code>'gnu'.between?('ant', 'dog')</code></td>
<td valign="top"></td>
<td valign="top"><code>false</code></td>
</tr>
</table>
<P></P>
<P></P>
</td></table>
<P></P>
<p></p><hr><table bgcolor="#a03030" cellpadding="10" border="0" cellspacing="0"><tr><td width="33%" align="left"><a class="subheader" href="ref_c_trueclass.html">Previous <</a></td><td width="33%" align="center" valign="middle"><a class="subheader" href="builtins.html">Contents ^</a><br></td><td width="33%" align="right"><a class="subheader" href="ref_m_enumerable.html">Next ></a><br></td></tr></table><p></p><font size="-1">Extracted from the book "Programming Ruby -
The Pragmatic Programmer's Guide"</font><br><font size="-3">
Copyright
©
2000 Addison Wesley Longman, Inc. Released under the terms of the
<a href="http://www.opencontent.org/openpub/">Open Publication License</a> V1.0.
<br>
This reference is available for
<a href="http://www.pragmaticprogrammer.com/ruby/downloads/book.html">download</a>.
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