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<HTML><HEAD><TITLE>5.1 The vector Data Abstraction</TITLE></HEAD><BODY><A HREF="ug1.htm"><IMG SRC="images/banner.gif"></A><BR><A HREF="vec_1893.htm"><IMG SRC="images/prev.gif"></A><A HREF="booktoc1.htm"><IMG SRC="images/toc.gif"></A><A HREF="tindex1.htm"><IMG SRC="images/tindex.gif"></A><A HREF="vec_6528.htm"><IMG SRC="images/next.gif"></A><BR><STRONG>Click on the banner to return to the user guide home page.</STRONG><H2>5.1 The vector Data Abstraction</H2><A NAME="idx47"><!></A><P>The <A HREF="../stdlibcr/vec_0251.htm"><B><I>vector</I></B></A> container class generalizes the concept of an ordinary C array. Like an array, a vector is an indexed data structure, with index values that range from 0 to one less than the number of elements contained in the structure. Also like an array, values are most commonly assigned to and extracted from the vector using the <SAMP>subscript</SAMP> operator. However, the vector differs from an array in the following important respects:</P><UL><LI>A vector has more "self-knowledge" than an ordinary array. In particular, a vector can be queried about its size, about the number of elements it can potentially hold (which may be different from its current size), and so on.</LI><LI>The size of the vector can change dynamically. New elements can be inserted on to the end of a vector, or into the middle. Storage management is handled efficiently and automatically. It is important to note, however, that while these abilities are provided, insertion into the middle of a vector is not as efficient as insertion into the middle of a <A HREF="../stdlibcr/lis_3222.htm"><B><I>list</I></B></A> (Section 6). If many insertion operations are to be performed, the <B><I>list</I></B> container should be used instead of the <A HREF="../stdlibcr/vec_0251.htm"><B><I>vector</I></B></A> data type.</LI></UL><P>The <A HREF="../stdlibcr/vec_0251.htm"><B><I>vector</I></B></A> container class in the standard library should be compared and contrasted to the <A HREF="../stdlibcr/deq_4164.htm"><B><I>deque</I></B></A> container class we will describe in more details in <A HREF="deq_4164.htm">Section 7.</A> Like a vector, a deque (pronounced "deck") is an indexed data structure. The major difference between the two is that a deque provides efficient insertion at either the beginning or the end of the container, while a vector provides efficient insertion only at the end. In many situations, either structure can be used. Use of a vector generally results in a smaller executable file, while, depending upon the particular set of operations being performed, use of a deque may result in a slightly faster program.</P><A NAME="5.1.1"><H3>5.1.1 Include Files</H3></A><P>Whenever you use a <A HREF="../stdlibcr/vec_0251.htm"><B><I>vector</I></B></A>, you must include the <SAMP>vector</SAMP> header file.</P><PRE> # include <vector></PRE><HR><A HREF="vec_1893.htm"><IMG SRC="images/prev.gif"></A> <A HREF="booktoc1.htm"><IMG SRC="images/toc.gif"></A><A HREF="tindex1.htm"><IMG SRC="images/tindex.gif"></A><A HREF="vec_6528.htm"><IMG SRC="images/next.gif"></A><P>©Copyright 1996, Rogue Wave Software, Inc.</P></BODY></HTML>⌨️ 快捷键说明
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