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<HTML><HEAD><TITLE>Foundation Classes</TITLE><SCRIPT>function setFocus() { if ((navigator.appName != "Netscape") && (parseFloat(navigator.appVersion) == 2)) { return; } else { self.focus(); }}</SCRIPT></HEAD><BODY BGCOLOR=#FFFFFF TEXT=#000000onLoad="setFocus()";><A NAME="top"></A><A NAME="chapter_foundation"></A><P>This appendix documents the foundation classes we use in the C++sample code of several design patterns. We've intentionally kept theclasses simple and minimal. We describe the following classes:</P><UL><A NAME="auto1000"></A><LI><A HREF="#secC-1"><CODE>List</CODE></A>, an ordered list of objects.</LI><A NAME="auto1001"></A><P></P><A NAME="auto1002"></A><LI><A HREF="#secC-2"><CODE>Iterator</CODE></A>,the interface for accessing an aggregate's objects in a sequence.</LI><A NAME="auto1003"></A><P></P><A NAME="auto1004"></A><LI><A HREF="#secC-3"><CODE>ListIterator</CODE></A>,an iterator for traversing a <CODE>List</CODE>.</LI><A NAME="auto1005"></A><P></P><A NAME="auto1006"></A><LI><A HREF="#secC-4"><CODE>Point</CODE></A>,a two-dimensional point.</LI><A NAME="auto1007"></A><P></P><A NAME="auto1008"></A><LI><A HREF="#secC-5"><CODE>Rect</CODE></A>, an axis-aligned rectangle.</LI></UL><A NAME="auto1009"></A><P>Some newer C++ standard types may not be available on allcompilers. In particular, if your compiler doesn't define<CODE>bool</CODE>, then define it manually as</P><A NAME="auto1010"></A><PRE> typedef int bool; const int true = 1; const int false = 0;</PRE><A NAME="secC-1"></A><H2><A HREF="#secC-2"><IMG SRC="gifsb/down3.gif" BORDER=0 ALT="next: Iterator"></A>List</H2><A NAME="auto1011"></A><P>The <CODE>List</CODE> class template provides a basic container forstoring an ordered list of objects. <CODE>List</CODE> stores elements byvalue, which means it works for built-in types as well as classinstances. For example, <CODE>List<int></CODE> declares a list of<CODE>int</CODE>s. But most of the patterns use <CODE>List</CODE> tostore pointers to objects, as in <CODE>List<Glyph*></CODE>. That way<CODE>List</CODE> can be used for heterogeneous lists.</P><A NAME="auto1012"></A><P>For convenience, <CODE>List</CODE> also provides synonyms for stackoperations, which make code that uses <CODE>List</CODE> for stacks moreexplicit without defining another class.</P><A NAME="auto1013"></A><PRE> template <class Item> class List { public: List(long size = DEFAULT_LIST_CAPACITY); List(List&); ~List(); List& operator=(const List&); long Count() const; Item& Get(long index) const; Item& First() const; Item& Last() const; bool Includes(const Item&) const; void Append(const Item&); void Prepend(const Item&); void Remove(const Item&); void RemoveLast(); void RemoveFirst(); void RemoveAll(); Item& Top() const; void Push(const Item&); Item& Pop(); };</PRE><A NAME="auto1014"></A><P>The following sections describe these operations in greater detail.</P><H3>Construction, Destruction, Initialization, and Assignment</H3><DL><DT><CODE>List(long size)</CODE></DT><DD>initializes the list. The <CODE>size</CODE> parameter is a hint forthe initial number of elements.</DD><A NAME="auto1015"></A><P></P><DT><CODE>List(List&)</CODE></DT><DD>overrides the default copy constructor so that member data areinitialized properly.</DD><A NAME="auto1016"></A><P></P><DT><CODE>~List()</CODE></DT><DD>frees the list's internal data structures but <EM>not</EM> theelements in the list. The class is not designed for subclassing;therefore the destructor isn't virtual.</DD><A NAME="auto1017"></A><P></P><DT><CODE>List& operator=(const List&)</CODE></DT><DD>implements the assignment operation to assign member data properly.</DD></DL><H3>Accessing</H3><A NAME="auto1018"></A><P>These operations provide basic access to the list's elements.<DL><DT><CODE>long Count() const</CODE></DT><DD>returns the number of objects in the list.</DD><A NAME="auto1019"></A><P></P><DT><CODE>Item& Get(long index) const</CODE></DT><DD>returns the object at the given index.</DD><A NAME="auto1020"></A><P></P><DT><CODE>Item& First() const</CODE></DT><DD>returns the first object in the list.</DD><A NAME="auto1021"></A><P></P><DT><CODE>Item& Last() const</CODE></DT><DD>returns the last object in the list.</DD></DL><H3>Adding</H3><DL><DT><CODE>void Append(const Item&)</CODE></DT><DD>adds the argument to the list, making it the last element.</DD><A NAME="auto1022"></A><P></P><DT><CODE>void Prepend(const Item&)</CODE></DT><DD>adds the argument to the list, making it the first element.</DD></DL><H3>Removing</H3><DL><DT><CODE>void Remove(const Item&)</CODE></DT><DD>removes the given element from the list. This operation requiresthat the type of elements in the list supports the<CODE>==</CODE> operator for comparison.</DD><A NAME="auto1023"></A><P></P><DT><CODE>void RemoveFirst()</CODE></DT><DD>removes the first element from the list.</DD><A NAME="auto1024"></A><P></P><DT><CODE>void RemoveLast()</CODE></DT><DD>removes the last element from the list.</DD><A NAME="auto1025"></A><P></P><DT><CODE>void RemoveAll()</CODE></DT><DD>removes all elements from the list.</DD></DL><H3>Stack Interface</H3><DL><DT><CODE>Item& Top() const</CODE></DT><DD>returns the top element (when the List is viewed as a stack).</DD><A NAME="auto1026"></A><P></P><DT><CODE>void Push(const Item&)</CODE></DT><DD>pushes the element onto the stack.</DD><A NAME="auto1027"></A><P></P><DT><CODE>Item& Pop()</CODE></DT><DD>pops the top element from the stack.</DD></DL><A NAME="secC-2"></A><H2><A HREF="#secC-3"><IMG SRC="gifsb/down3.gif" BORDER=0 ALT="next: ListIterator"></A>Iterator</H2><A NAME="auto1028"></A><P><CODE>Iterator</CODE> is an abstract class that defines a traversalinterface for aggregates.</P><A NAME="auto1029"></A><PRE> template <class Item> class Iterator { public: virtual void First() = 0; virtual void Next() = 0; virtual bool IsDone() const = 0; virtual Item CurrentItem() const = 0; protected: Iterator(); };</PRE><A NAME="auto1030"></A><P>The operations do the following:</P><DL><DT><CODE>virtual void First()</CODE></DT><DD>positions the iterator to the first object in the aggregate.</DD><A NAME="auto1031"></A><P></P><DT><CODE>virtual void Next()</CODE></DT><DD>positions the iterator to the next object in the sequence.</DD><A NAME="auto1032"></A><P></P><DT><CODE>virtual bool IsDone() const</CODE></DT><DD>returns <CODE>true</CODE> when there are no more objects in the sequence.</DD><A NAME="auto1033"></A><P></P><DT><CODE>virtual Item CurrentItem() const</CODE></DT><DD>returns the object at the current position in the sequence.</DD></DL><A NAME="secC-3"></A><H2><A HREF="#secC-4"><IMG SRC="gifsb/down3.gif" BORDER=0 ALT="next: Point"></A>ListIterator</H2><A NAME="auto1034"></A><P><CODE>ListIterator</CODE> implements the <CODE>Iterator</CODE> interfaceto traverse List objects. Its constructor takes a list to traverse asan argument.</P><A NAME="auto1035"></A><PRE> template <class Item> class ListIterator : public Iterator<Item> { public: ListIterator(const List<Item>* aList); virtual void First(); virtual void Next(); virtual bool IsDone() const; virtual Item CurrentItem() const; };</PRE><A NAME="secC-4"></A><H2><A HREF="#secC-5"><IMG SRC="gifsb/down3.gif" BORDER=0 ALT="next: Rect"></A>Point</H2><A NAME="auto1036"></A><P><CODE>Point</CODE> represents a point in a two-dimensional Cartesiancoordinate space. <CODE>Point</CODE> supports some minimal vector arithmetic.The coordinates of a <CODE>Point</CODE> are defined as</P><A NAME="auto1037"></A><PRE> typedef float Coord;</PRE><A NAME="auto1038"></A><P><CODE>Point</CODE>'s operations are self-explanatory.</P><A NAME="auto1039"></A><PRE> class Point { public: static const Point Zero; Point(Coord x = 0.0, Coord y = 0.0); Coord X() const; void X(Coord x); Coord Y() const; void Y(Coord y); friend Point operator+(const Point&, const Point&); friend Point operator-(const Point&, const Point&); friend Point operator*(const Point&, const Point&); friend Point operator/(const Point&, const Point&); Point& operator+=(const Point&); Point& operator-=(const Point&); Point& operator*=(const Point&); Point& operator/=(const Point&); Point operator-(); friend bool operator==(const Point&, const Point&); friend bool operator!=(const Point&, const Point&); friend ostream& operator<<(ostream&, const Point&); friend istream& operator>>(istream&, Point&); };</PRE><A NAME="auto1040"></A><P>The static member <CODE>Zero</CODE> represents <CODE>Point(0, 0)</CODE>.<A NAME="secC-5"></A><H2><A HREF="#last"><IMG SRC="gifsb/down3.gif" BORDER=0 ALT="next: navigation"></A>Rect</H2><A NAME="auto1041"></A><P><CODE>Rect</CODE> represents an axis-aligned rectangle. A<CODE>Rect</CODE> is defined by an origin point and an extent (thatis, width and height). The <CODE>Rect</CODE> operations areself-explanatory.</P><A NAME="auto1042"></A><PRE> class Rect { public: static const Rect Zero; Rect(Coord x, Coord y, Coord w, Coord h); Rect(const Point& origin, const Point& extent); Coord Width() const; void Width(Coord); Coord Height() const; void Height(Coord); Coord Left() const; void Left(Coord); Coord Bottom() const; void Bottom(Coord); Point& Origin() const; void Origin(const Point&); Point& Extent() const; void Extent(const Point&); void MoveTo(const Point&); void MoveBy(const Point&); bool IsEmpty() const; bool Contains(const Point&) const; };</PRE><A NAME="auto1043"></A><P>The static member <CODE>Zero</CODE> is equivalent to the rectangle</P><A NAME="auto1044"></A><PRE> Rect(Point(0, 0), Point(0, 0));</PRE><A NAME="last"></A><P><A HREF="#top"><IMG SRC="gifsb/up3.gif" BORDER=0></A><BR><A HREF="bibfs.htm" TARGET="_mainDisplayFrame"><IMG SRC="gifsb/rightar3.gif" ALIGN=TOP BORDER=0></A> <A HREF="bibfs.htm" TARGET="_mainDisplayFrame">Bibliography</A><BR><A HREF="chapBfs.htm" TARGET="_mainDisplayFrame"><IMG SRC="gifsb/leftarr3.gif" ALIGN=TOP BORDER=0></A> <A HREF="chapBfs.htm" TARGET="_mainDisplayFrame">Guide to Notation</A></P></BODY></HTML>?? 快捷鍵說明
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