<?xml version="1.0" encoding="utf-8"?>
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<part xml:id="spl.datastructures" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">

 &spl.datastructures.intro.title;

 <partintro>
  <para>
   SPL provides a set of standard datastructures. They are grouped here by their 
   underlying implementation which usually defines their general field of 
   application.
  </para>

  <section>
   <title>Doubly Linked Lists</title>

   <para>
    A Doubly Linked List (DLL) is a list of nodes linked in both directions to 
    each other. Iterator's operations, access to both ends, addition or 
    removal of nodes have a cost of O(1) when the underlying structure is a DLL.
    It hence provides a decent implementation for stacks and queues.
   </para>

   <itemizedlist>
    <listitem>
     <simpara><classname>SplDoublyLinkedList</classname></simpara>
     <itemizedlist>
      <listitem><simpara><classname>SplStack</classname></simpara></listitem>
      <listitem><simpara><classname>SplQueue</classname></simpara></listitem>
     </itemizedlist>
    </listitem>
   </itemizedlist>

  </section>
  <section>
   <title>Heaps</title>

   <para>
    Heaps are tree-like structures that follow the heap-property: each node
    is greater than or equal to its children, when compared using the 
    implemented compare method which is global to the heap.
   </para>

   <itemizedlist>
    <listitem>
     <simpara><classname>SplHeap</classname></simpara>
     <itemizedlist>
      <listitem><simpara><classname>SplMaxHeap</classname></simpara></listitem>
      <listitem><simpara><classname>SplMinHeap</classname></simpara></listitem>
     </itemizedlist>
    </listitem>
    <listitem>
     <simpara><classname>SplPriorityQueue</classname></simpara>
    </listitem>
   </itemizedlist>

  </section>

  <section>
   <title>Arrays</title>

   <para>
    Arrays are structures that store the data in a continuous way, accessible
    via indexes. Don't confuse them with PHP arrays: PHP arrays are in fact 
    implemented as ordered hashtables.
   </para>

   <itemizedlist>
    <listitem>
     <simpara><classname>SplFixedArray</classname></simpara>
    </listitem>
   </itemizedlist>

  </section>

  <section>
   <title>Map</title>

   <para>
    A map is a datastructure holding key-value pairs. PHP arrays can be seen as maps from integers/strings to values. SPL provides a map from objects to data. This map can also be used as an object set.
   </para>

   <itemizedlist>
    <listitem>
     <simpara><classname>SplObjectStorage</classname></simpara>
    </listitem>
   </itemizedlist>

  </section>
 </partintro>

 &reference.spl.spldoublylinkedlist;
 &reference.spl.splstack;
 &reference.spl.splqueue;

 &reference.spl.splheap;
 &reference.spl.splmaxheap;
 &reference.spl.splminheap;
 &reference.spl.splpriorityqueue;

 &reference.spl.splfixedarray;
 &reference.spl.splobjectstorage;

</part>



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