125 lines
4.5 KiB
XML
125 lines
4.5 KiB
XML
<chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
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xml:id="std.util" xreflabel="Utilities">
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<?dbhtml filename="utilities.html"?>
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<info><title>
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Utilities
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<indexterm><primary>Utilities</primary></indexterm>
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</title>
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<keywordset>
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<keyword>
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ISO C++
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</keyword>
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<keyword>
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library
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</keyword>
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</keywordset>
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</info>
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<!-- Section 01 : Functors -->
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<section xml:id="std.util.functors" xreflabel="Functors"><info><title>Functors</title></info>
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<?dbhtml filename="functors.html"?>
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<para>If you don't know what functors are, you're not alone. Many people
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get slightly the wrong idea. In the interest of not reinventing
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the wheel, we will refer you to the introduction to the functor
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concept written by SGI as chapter of their STL, in
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<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.sgi.com/tech/stl/functors.html">their
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http://www.sgi.com/tech/stl/functors.html</link>.
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</para>
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</section>
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<!-- Section 02 : Pairs -->
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<section xml:id="std.util.pairs" xreflabel="Pairs"><info><title>Pairs</title></info>
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<?dbhtml filename="pairs.html"?>
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<para>The <code>pair<T1,T2></code> is a simple and handy way to
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carry around a pair of objects. One is of type T1, and another of
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type T2; they may be the same type, but you don't get anything
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extra if they are. The two members can be accessed directly, as
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<code>.first</code> and <code>.second</code>.
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</para>
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<para>Construction is simple. The default ctor initializes each member
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with its respective default ctor. The other simple ctor,
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</para>
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<programlisting>
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pair (const T1& x, const T2& y);
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</programlisting>
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<para>does what you think it does, <code>first</code> getting <code>x</code>
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and <code>second</code> getting <code>y</code>.
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</para>
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<para>There is a copy constructor, but it requires that your compiler
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handle member function templates:
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</para>
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<programlisting>
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template <class U, class V> pair (const pair<U,V>& p);
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</programlisting>
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<para>The compiler will convert as necessary from U to T1 and from
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V to T2 in order to perform the respective initializations.
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</para>
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<para>The comparison operators are done for you. Equality
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of two <code>pair<T1,T2></code>s is defined as both <code>first</code>
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members comparing equal and both <code>second</code> members comparing
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equal; this simply delegates responsibility to the respective
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<code>operator==</code> functions (for types like MyClass) or builtin
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comparisons (for types like int, char, etc).
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</para>
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<para>
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The less-than operator is a bit odd the first time you see it. It
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is defined as evaluating to:
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</para>
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<programlisting>
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x.first < y.first ||
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( !(y.first < x.first) && x.second < y.second )
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</programlisting>
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<para>The other operators are not defined using the <code>rel_ops</code>
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functions above, but their semantics are the same.
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</para>
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<para>Finally, there is a template function called <function>make_pair</function>
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that takes two references-to-const objects and returns an
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instance of a pair instantiated on their respective types:
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</para>
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<programlisting>
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pair<int,MyClass> p = make_pair(4,myobject);
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</programlisting>
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</section>
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<!-- Section 03 : Memory -->
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<section xml:id="std.util.memory" xreflabel="Memory"><info><title>Memory</title></info>
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<?dbhtml filename="memory.html"?>
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<para>
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Memory contains three general areas. First, function and operator
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calls via <function>new</function> and <function>delete</function>
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operator or member function calls. Second, allocation via
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<classname>allocator</classname>. And finally, smart pointer and
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intelligent pointer abstractions.
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</para>
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<!-- Section 01 : allocator -->
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<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" parse="xml" href="allocator.xml">
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</xi:include>
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<!-- Section 02 : auto_ptr -->
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<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" parse="xml" href="auto_ptr.xml">
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</xi:include>
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<!-- Section 03 : shared_ptr -->
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<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" parse="xml" href="shared_ptr.xml">
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</xi:include>
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</section>
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<!-- Section 04 : Traits -->
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<section xml:id="std.util.traits" xreflabel="Traits"><info><title>Traits</title></info>
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<?dbhtml filename="traits.html"?>
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<para>
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</para>
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</section>
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</chapter>
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