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      1 <chapter xmlns="http://docbook.org/ns/docbook" version="5.0"
      2 	 xml:id="std.util" xreflabel="Utilities">
      3 <?dbhtml filename="utilities.html"?>
      4 
      5 <info><title>
      6   Utilities
      7   <indexterm><primary>Utilities</primary></indexterm>
      8 </title>
      9   <keywordset>
     10     <keyword>ISO C++</keyword>
     11     <keyword>library</keyword>
     12   </keywordset>
     13 </info>
     14 
     15 
     16 
     17 <!-- Section 01 : Functors -->
     18 <section xml:id="std.util.functors" xreflabel="Functors"><info><title>Functors</title></info>
     19 <?dbhtml filename="functors.html"?>
     20 
     21    <para>If you don't know what functors are, you're not alone.  Many people
     22       get slightly the wrong idea.  In the interest of not reinventing
     23       the wheel, we will refer you to the introduction to the functor
     24       concept written by SGI as part of their STL, in
     25       <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://web.archive.org/web/20171225062613/http://www.sgi.com/tech/stl/functors.html">their
     26       https://web.archive.org/web/20171225062613/http://www.sgi.com/tech/stl/functors.html</link>.
     27    </para>
     28 </section>
     29 
     30 <!-- Section 02 : Pairs -->
     31 <section xml:id="std.util.pairs" xreflabel="Pairs"><info><title>Pairs</title></info>
     32 <?dbhtml filename="pairs.html"?>
     33 
     34    <para>The <code>pair&lt;T1,T2&gt;</code> is a simple and handy way to
     35       carry around a pair of objects.  One is of type T1, and another of
     36       type T2; they may be the same type, but you don't get anything
     37       extra if they are.  The two members can be accessed directly, as
     38       <code>.first</code> and <code>.second</code>.
     39    </para>
     40    <para>Construction is simple.  The default ctor initializes each member
     41       with its respective default ctor.  The other simple ctor,
     42    </para>
     43    <programlisting>
     44     pair (const T1&amp; x, const T2&amp; y);
     45    </programlisting>
     46    <para>does what you think it does, <code>first</code> getting <code>x</code>
     47       and <code>second</code> getting <code>y</code>.
     48    </para>
     49    <para>There is a constructor template for copying pairs of other types:
     50    </para>
     51    <programlisting>
     52     template &lt;class U, class V&gt; pair (const pair&lt;U,V&gt;&amp; p);
     53    </programlisting>
     54    <para>The compiler will convert as necessary from U to T1 and from
     55       V to T2 in order to perform the respective initializations.
     56    </para>
     57    <para>The comparison operators are done for you.  Equality
     58       of two <code>pair&lt;T1,T2&gt;</code>s is defined as both <code>first</code>
     59       members comparing equal and both <code>second</code> members comparing
     60       equal; this simply delegates responsibility to the respective
     61       <code>operator==</code> functions (for types like MyClass) or builtin
     62       comparisons (for types like int, char, etc).
     63    </para>
     64    <para>
     65       The less-than operator is a bit odd the first time you see it.  It
     66       is defined as evaluating to:
     67    </para>
     68    <programlisting>
     69     x.first  &lt;  y.first  ||
     70 	( !(y.first  &lt;  x.first)  &amp;&amp;  x.second  &lt;  y.second )
     71    </programlisting>
     72    <para>The other operators are not defined using the <code>rel_ops</code>
     73       functions above, but their semantics are the same.
     74    </para>
     75    <para>Finally, there is a template function called <function>make_pair</function>
     76       that takes two references-to-const objects and returns an
     77       instance of a pair instantiated on their respective types:
     78    </para>
     79    <programlisting>
     80     pair&lt;int,MyClass&gt; p = make_pair(4,myobject);
     81    </programlisting>
     82 
     83 </section>
     84 
     85 <!-- Section 03 : Memory -->
     86 <section xml:id="std.util.memory" xreflabel="Memory"><info><title>Memory</title></info>
     87 <?dbhtml filename="memory.html"?>
     88 
     89   <para>
     90     Memory contains three general areas. First, function and operator
     91     calls via <function>new</function> and <function>delete</function>
     92     operator or member function calls.  Second, allocation via
     93     <classname>allocator</classname>. And finally, smart pointer and
     94     intelligent pointer abstractions.
     95   </para>
     96 
     97   <!--  Section 01 : allocator -->
     98   <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" parse="xml" href="allocator.xml">
     99   </xi:include>
    100 
    101   <!--  Section 02 : auto_ptr -->
    102   <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" parse="xml" href="auto_ptr.xml">
    103   </xi:include>
    104 
    105   <!--  Section 03 : shared_ptr -->
    106   <xi:include xmlns:xi="http://www.w3.org/2001/XInclude" parse="xml" href="shared_ptr.xml">
    107   </xi:include>
    108 
    109 </section>
    110 
    111 <!-- Section 04 : Traits -->
    112 <section xml:id="std.util.traits" xreflabel="Traits"><info><title>Traits</title></info>
    113 <?dbhtml filename="traits.html"?>
    114 
    115   <para>
    116   </para>
    117 </section>
    118 
    119 </chapter>
    120