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<b>Data Structures and Algorithms
with Object-Oriented Design Patterns in C++</b><br>
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<H1><A NAME="SECTION006300000000000000000">Exercises</A></H1>
<P>
<OL><LI>
Specify the set of values and the set of operations
provided by each of the following C++ built-in data types:
<OL><LI> <tt>char</tt>,<LI> <tt>int</tt>,<LI> <tt>double</tt>, and<LI> <tt>string</tt>.
</OL><LI>
What are the features of C++ that
facilitate the creation of <em>user-defined</em> data types.<LI>
Explain how each of the following
C++ features supports <em>polymorphism</em>:
<OL><LI> operator overloading,<LI> templates, and<LI> inheritance.
</OL><LI>
Suppose we define two concrete classes, <tt>A</tt> and <tt>B</tt>,
both of which are derived from the <tt>Object</tt> class
declared in Program <A HREF="page111.html#progobject1h" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page111.html#progobject1h"><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>.
Furthermore, let <tt>a</tt> and <tt>b</tt> be instances of
classes <tt>A</tt> and <tt>B</tt> (respectively) declared as follows:
<PRE>class A : public Object { ... };
class B : public Object { ... };
A a;
B b;</PRE>
Give the sequence of functions called in order to evaluate
a comparison such as ``<tt>a<b</tt>''.
Is the result of the comparison <tt>true</tt> or <tt>false</tt>?
Explain.<LI>
Consider the <tt>Wrapper<T></tt> class defined in Program <A HREF="page115.html#progwrapper1h" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page115.html#progwrapper1h"><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>.
Explain the operation of the following program fragment:
<PRE>int i = 5;
Wrapper<int> j = 7;
i = j;
j = i;</PRE><LI>
There are three ways to test whether a given object instance,
<tt>obj</tt>, is the null object:
<OL><LI> <tt>obj.IsNull ()</tt><LI> <tt>obj == NullObject::Instance ()</tt>, and<LI> <tt>&obj == &(NullObject::Instance ())</tt>.
</OL>
Discuss the relative merits of each approach.<LI>
Let <tt>c</tt> be an instance of some concrete class
derived from the <tt>Container</tt> class
given in Program <A HREF="page117.html#progcontainer1h" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page117.html#progcontainer1h"><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>.
Explain how the statement
<PRE>cout << c;</PRE>
prints the contents of the container
on the standard output stream, <tt>cout</tt>.<LI>
Suppose we have a container <tt>c</tt>
(i.e., an instance of some concrete class
derived from the <tt>Container</tt> class
defined in Program <A HREF="page117.html#progcontainer1h" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page117.html#progcontainer1h"><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>)
which among other things happens to contain itself.
Is it permissible for <tt>c</tt> to own the objects it contains?
What happens when <tt>c</tt>'s destructor runs
if it owns the objects it contains.<LI>
Iterators and visitors provide two ways to do the same thing--to visit one-by-one all the objects in a container.
Give an implementation for the <tt>Accept</tt> function
of the <tt>Container</tt> class that uses an iterator.<LI>
Is it possible to implement an iterator using a visitor?
Explain.<LI>
Suppose we have a container which we know contains only
instances of the <tt>Int</tt> class defined in Program <A HREF="page116.html#progwrapper2h" tppabs="http://dictator.uwaterloo.ca/Bruno.Preiss/books/opus4/html/page116.html#progwrapper2h"><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>.
Design a <tt>Visitor</tt> which computes the sum of all the integers
in the container.<LI>
Explain what the following visitor does
and why it is a horribly bad idea:
<PRE>class DeletingVisitor : public Visitor
{
public:
void Visit (Object& object)
{ delete &object; }
};</PRE><LI>
Consider the following pair of <tt>Association</tt>s:
<PRE>Association a (*new Int (3), *new Int (4));
Association b (*new Int (3));</PRE>
Give the sequence of functions called in order to evaluate
a comparison such as ``<tt>a==b</tt>''.
Is the result of the comparison <tt>true</tt> or <tt>false</tt>?
Explain.
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