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<ppdoc>
<copyright>
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/).
</copyright>
<class name="Comparable" type="module">
<p/>
<relieson><tt><=></tt></relieson> The <modulename>Comparable</modulename> mixin is used by classes whose objects may be
ordered. The class must define the <tt><=></tt>
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. <modulename>Comparable</modulename> uses <tt><=></tt> to implement the
conventional comparison operators (<tt><</tt>, <tt><=</tt>, <tt>==</tt>,
<tt>>=</tt>, and <tt>></tt>) and the method <meth>between?</meth>.
<p/>
<codefragment>
<fullcode><![CDATA[ class SizeMatters
include Comparable
attr :str
def <=>(anOther)
str.size <=> anOther.str.size
end
def initialize(str)
@str = str
end
def inspect
@str
end
end
s1 = SizeMatters.new("Z")
s2 = SizeMatters.new("YY")
s3 = SizeMatters.new("XXX")
s4 = SizeMatters.new("WWWW")
s5 = SizeMatters.new("VVVVV")
s1 < s2
s4.between?(s1, s3)
s4.between?(s3, s5)
[ s3, s2, s5, s4, s1 ].sort
]]></fullcode><rubycode>
<tr>
<td colspan="3"><tt>class<nbsp/>SizeMatters</tt></td>
</tr>
<tr>
<td colspan="3"><tt><nbsp/><nbsp/>include<nbsp/>Comparable</tt></td>
</tr>
<tr>
<td colspan="3"><tt><nbsp/><nbsp/>attr<nbsp/>:str</tt></td>
</tr>
<tr>
<td colspan="3"><tt><nbsp/><nbsp/>def<nbsp/><=>(anOther)</tt></td>
</tr>
<tr>
<td colspan="3"><tt><nbsp/><nbsp/><nbsp/><nbsp/>str.size<nbsp/><=><nbsp/>anOther.str.size</tt></td>
</tr>
<tr>
<td colspan="3"><tt><nbsp/><nbsp/>end</tt></td>
</tr>
<tr>
<td colspan="3"><tt><nbsp/><nbsp/>def<nbsp/>initialize(str)</tt></td>
</tr>
<tr>
<td colspan="3"><tt><nbsp/><nbsp/><nbsp/><nbsp/>@str<nbsp/>=<nbsp/>str</tt></td>
</tr>
<tr>
<td colspan="3"><tt><nbsp/><nbsp/>end</tt></td>
</tr>
<tr>
<td colspan="3"><tt><nbsp/><nbsp/>def<nbsp/>inspect</tt></td>
</tr>
<tr>
<td colspan="3"><tt><nbsp/><nbsp/><nbsp/><nbsp/>@str</tt></td>
</tr>
<tr>
<td colspan="3"><tt><nbsp/><nbsp/>end</tt></td>
</tr>
<tr>
<td colspan="3"><tt>end</tt></td>
</tr>
<tr>
<td colspan="3"><tt></tt></td>
</tr>
<tr>
<td colspan="3"><tt>s1<nbsp/>=<nbsp/>SizeMatters.new("Z")</tt></td>
</tr>
<tr>
<td colspan="3"><tt>s2<nbsp/>=<nbsp/>SizeMatters.new("YY")</tt></td>
</tr>
<tr>
<td colspan="3"><tt>s3<nbsp/>=<nbsp/>SizeMatters.new("XXX")</tt></td>
</tr>
<tr>
<td colspan="3"><tt>s4<nbsp/>=<nbsp/>SizeMatters.new("WWWW")</tt></td>
</tr>
<tr>
<td colspan="3"><tt>s5<nbsp/>=<nbsp/>SizeMatters.new("VVVVV")</tt></td>
</tr>
<tr>
<td colspan="3"><tt></tt></td>
</tr>
<tr>
<td><tt>s1<nbsp/><<nbsp/>s2</tt></td>
<td>»</td>
<td><tt>true</tt></td>
</tr>
<tr>
<td><tt>s4.between?(s1,<nbsp/>s3)</tt></td>
<td>»</td>
<td><tt>false</tt></td>
</tr>
<tr>
<td><tt>s4.between?(s3,<nbsp/>s5)</tt></td>
<td>»</td>
<td><tt>true</tt></td>
</tr>
<tr>
<td><tt>[<nbsp/>s3,<nbsp/>s2,<nbsp/>s5,<nbsp/>s4,<nbsp/>s1<nbsp/>].sort</tt></td>
<td>»</td>
<td><tt>[Z,<nbsp/>YY,<nbsp/>XXX,<nbsp/>WWWW,<nbsp/>VVVVV]</tt></td>
</tr>
</rubycode>
<p/>
</codefragment>
<p/>
<methods type="instance">
<p/>
<method name="Comparisons" ref="Comparisons">
<callseq>
<obj>anObject</obj> < <obj>otherObject</obj> <returns><const>true</const> or <const>false</const></returns><br/><obj>anObject</obj> <= <obj>otherObject</obj> <returns><const>true</const> or <const>false</const></returns><br/><obj>anObject</obj> == <obj>otherObject</obj> <returns><const>true</const> or <const>false</const></returns><br/><obj>anObject</obj> >= <obj>otherObject</obj> <returns><const>true</const> or <const>false</const></returns><br/><obj>anObject</obj> > <obj>otherObject</obj> <returns><const>true</const> or <const>false</const></returns><br/>
</callseq>
<desc>
<p/>
Compares two objects based on the receiver's <meth><=></meth> method.
<p/>
</desc>
</method>
<p/>
<method name="between?" ref="between_qm">
<callseq>
<obj>anObject</obj>.between?( <obj>min</obj>, <obj>max</obj> )
<returns><const>true</const> or <const>false</const></returns>
</callseq>
<desc>
<p/>
Returns <const>false</const> if <obj>anObject</obj><nbsp/><tt><=></tt><nbsp/><obj>min</obj> is less than
zero or if <obj>anObject</obj><nbsp/><tt><=></tt><nbsp/><obj>max</obj> is greater than zero,
<const>true</const> otherwise.
<p/>
<codefragment>
<fullcode><![CDATA[ 3.between?(1, 5)
6.between?(1, 5)
'cat'.between?('ant', 'dog')
'gnu'.between?('ant', 'dog')
]]></fullcode><rubycode>
<tr>
<td><tt>3.between?(1,<nbsp/>5)</tt></td>
<td>»</td>
<td><tt>true</tt></td>
</tr>
<tr>
<td><tt>6.between?(1,<nbsp/>5)</tt></td>
<td>»</td>
<td><tt>false</tt></td>
</tr>
<tr>
<td><tt>'cat'.between?('ant',<nbsp/>'dog')</tt></td>
<td>»</td>
<td><tt>true</tt></td>
</tr>
<tr>
<td><tt>'gnu'.between?('ant',<nbsp/>'dog')</tt></td>
<td>»</td>
<td><tt>false</tt></td>
</tr>
</rubycode>
<p/>
</codefragment>
<p/>
</desc>
</method>
<p/>
</methods>
<p/>
</class>
</ppdoc>
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