📄 page146.html

📁 wqeqwvrw rkjqhwrjwq jkhrjqwhrwq jkhrwq
💻 HTML
字号:
<HTML>
<HEAD>
<TITLE>Implementation</TITLE>
</HEAD>
<BODY bgcolor="#FFFFFF">
 <img src="cover75.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/cover75.gif" alt="Logo" align=right>
<b>Data Structures and Algorithms 
with Object-Oriented Design Patterns in C++</b><br>
<A NAME="tex2html3712" HREF="page147.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page147.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="next_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/next_motif.gif"></A> <A NAME="tex2html3710" HREF="page144.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page144.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="up_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/up_motif.gif"></A> <A NAME="tex2html3706" HREF="page145.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page145.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="previous_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/previous_motif.gif"></A> <A NAME="tex2html3714" HREF="page9.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page9.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/contents_motif.gif"></A> <A NAME="tex2html3715" HREF="page620.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page620.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="index_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/index_motif.gif"></A> <BR><HR>
<H3><A NAME="SECTION007132000000000000000">Implementation</A></H3>
<P>
Program&nbsp;<A HREF="page146.html#progapp01c" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page146.html#progapp01c"><IMG  ALIGN=BOTTOM ALT="gif" SRC="cross_ref_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/cross_ref_motif.gif"></A> gives the implementation of a simple RPN calculator.
The purpose of this example
is to illustrate the use of the <tt>Stack</tt> class.
The program shown accepts very simplified RPN expressions:
The expression may contain only single-digit integers,
the addition operator, <tt>+</tt>,
and the multiplication operator, <tt>*</tt>.
In addition, the operator <tt>=</tt> pops the top value off the stack
and prints it on the standard output stream, <tt>cout</tt>.
Furthermore, the calculator does its computation entirely with integers.
<P>
<P><A NAME="6594">&#160;</A><A NAME="progapp01c">&#160;</A> <IMG WIDTH=575 HEIGHT=601 ALIGN=BOTTOM ALT="program6591" SRC="img734.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/img734.gif"  ><BR>
<STRONG>Program:</STRONG> Stack Application--A Single-Digit, RPN Calculator<BR>
<P>
<P>
Notice that the <tt>RPNCalculator</tt> function
is passed a reference to a <tt>Stack</tt> object.
Consequently, the function manipulates the stack entirely through
the abstract interface.
The calculator does not depend on the stack implementation used!
For example, if we wish to use a stack implemented using an array,
we would declare a <tt>StackAsArray</tt> variable and invoke the
calculator as follows:
<PRE>StackAsArray s (10);
RPNCalculator (s);</PRE>
On the other hand, if we decided to use the pointer-based stack implementation,
we would write:
<PRE>StackAsLinkedList s;
RPNCalculator (s);</PRE>
<P>
The running time of the <tt>RPNCalculator</tt> function depends
upon the number of symbols, operators and operands,
in the expression being evaluated.
If there are <I>n</I> symbols,
the body of the <tt>for</tt> loop is executed <I>n</I> times.
It should be fairly obvious that the amount of work done
per symbol is constant, regardless of the type of symbol encountered.
This is the case for both the <tt>StackAsArray</tt>
and the <tt>StackAsLinkedList</tt> stack implementations.
Therefore, the total running time needed to evaluate an
expression comprised of <I>n</I> symbols is <I>O</I>(<I>n</I>).
<P>
<HR><A NAME="tex2html3712" HREF="page147.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page147.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="next_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/next_motif.gif"></A> <A NAME="tex2html3710" HREF="page144.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page144.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="up_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/up_motif.gif"></A> <A NAME="tex2html3706" HREF="page145.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page145.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="previous_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/previous_motif.gif"></A> <A NAME="tex2html3714" HREF="page9.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page9.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/contents_motif.gif"></A> <A NAME="tex2html3715" HREF="page620.html" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page620.html"><IMG WIDTH=43 HEIGHT=24 ALIGN=BOTTOM ALT="index" SRC="index_motif.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/index_motif.gif"></A> <P><ADDRESS>
<img src="bruno.gif" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/icons/bruno.gif" alt="Bruno" align=right>
<a href="javascript:if(confirm('http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/copyright.html  \n\nThis file was not retrieved by Teleport Pro, because it is addressed on a domain or path outside the boundaries set for its Starting Address.  \n\nDo you want to open it from the server?'))window.location='http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/copyright.html'" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/copyright.html">Copyright &#169; 1997</a> by <a href="javascript:if(confirm('http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/signature.html  \n\nThis file was not retrieved by Teleport Pro, because it is addressed on a domain or path outside the boundaries set for its Starting Address.  \n\nDo you want to open it from the server?'))window.location='http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/signature.html'" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/signature.html">Bruno R. Preiss, P.Eng.</a>  All rights reserved.

</ADDRESS>
</BODY>
</HTML>
⌨️ 快捷键说明

复制代码 Ctrl + C
搜索代码 Ctrl + F
全屏模式 F11
切换主题 Ctrl + Shift + D
显示快捷键 ?
增大字号 Ctrl + =
减小字号 Ctrl + -