Chapter 15 C Function

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Chapter 15 C Function

• By C. Shing
• ITEC Dept
• Radford University

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Objectives

• Understand how to create and free dynamic
• memory
• Understand the scope rule
• Understand pass by reference
• Understand member functions
• Know how to write inline functions
• Understand function overloading
• Understand static function
• Understand template function and virtual function

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Dynamic Memory

• Create a memory pointed by memPtr
• (calls constructor)
• Form type memPtrnew type
• Example int numberPtrnew int
• Destroy the dynamic memory memPtr
• (calls destructor)
• Form delete memPtr
• Example delete memPtr

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Dynamic Memory (Cont.)

• Create an array of memory
• pointed by arrayPtr
• Form type arrayPtrnew typeSIZE
• Example int numberarrayPtrnew intSIZE
• Destroy the dynamic array memory arrayPtr
• Form delete arrayPtr
• Example delete numberarrayPtr

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Scope Rule

• The variable is meaningful and unique
• in its defined block
• The local variable redefined scope precedes
• the global variable if use the same name.
• The global variable can be referred using
• local variable name

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Scope Rule (Cont.)

• Example
• int number 10
• Int main()
• int number 100
• cout ltlt local number ltltnumber
• cout ltlt global number ltltnumber

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Pass By Reference

• The function directly access the variables passed
• in using reference.
• (This is different from passing pointers)

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Pass By Reference (Cont.)

• Example
• Int main()
• int number10
• byRef(number)
• cout ltlt number // print 100
• void byRef(int number)
• number100

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Pass By Reference - Example

• Array of Pointers Store array of strings
• Assume that array w has 5 cells, each stores an
• address of strings as follows
• w0100address of string this
• w1200address of string is
• w2300address of string a
• w3400address of string snow
• w4500address of string day

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Pass By Reference Example (Cont.)

• Bubble sort for array w
• To call sort_strings sort_strings(w, size)
• To use bubble sort to sort the array w
• void sort_strings (char w, int n)
• int i, j
• for (i0 iltn i)
• for (ji1 jltnj)
• if (strcmp(wi,wj)gt0)
• swap (wi, wj)

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Pass By Reference Example (Cont.)

• Example (Cont.) You may also write it as
• void swap (char s, char t)
• char tmp
• tmps
• st
• ttmp

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Pass By Reference Example (Cont.)

• Without using class
• bubble.cpp
• bubble_data.txt
• Using class
• bubbleclass.cpp
• bubble_data.txt

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Pass By Pointer Example (Cont.)

• Bubble sort for array w
• To use bubble sort to sort the array w
• void sort_strings (char w, int n)
• int i, j
• for (i0 iltn i)
• for (ji1 jltnj)
• if (strcmp(wi,wj)gt0)
• swap (wi, wj)

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Pass By Pointer Example (Cont.)

• Example (Cont.) The swap function is
• void swap (char s, char t)
• char tmp
• tmps
• st
• ttmp

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Pass By Pointer Example (Cont.)

• Using class
• bubbleclassPtr.cpp
• bubble_data.txt

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Functions

• member functions
• only functions that can access member in the
  class
• Default constructor missing parameters will be
• initialized automatically by the default values
• inline function
• short function that can fit in one line
• constant function function that does not change
  any
• member data, not allowed for constructor or
  destructor.
• A non-constant function is not allowed to
  access
• constant object.

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Functions (Cont.)

• friend function
• not a member function but can access member
• data
• static function (no this pointer available)
• function that returns
• static variable (share among all objects
  created)
• without any object exists

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Functions (Cont.)

• Overloading
• Function overloading function with different
• argument list, each function performs different
• task
• Operator overloading rewrite rule for existing
• operator on object (not change operator
  precedence
• nor the operator characteristics)

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Functions (Cont.)

• Template
• Template function same task for different
• data types
• Class template specify template for entire class
  member data
• and member functions

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Functions (Cont.)

• Virtual function used to specify interface
• function and will be implemented in various
• inherited classes (discussed in Polymorphism)

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Member Function Default Constructor

• Form
• Class Name (type default value, )
• Example
• default constructor for 2D Point class
• Point (int0, int0)

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Member function - inline

• Example
• Class 3DPoint
• public
• 3DPoint(double 0.0, double 0.0,
• double 0.0)
• double getX() return x // this is inline
  function
• private
• double x, y, z

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Member function - constant

• Example
• Class 3DPoint
• public
• 3DPoint(double 0.0, double 0.0,
• double 0.0)
• double getX() const return x // constant
  function
• private
• double x, y, z

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Member function inline and constant function
Example

• Using class a 3D Point class
• point.cpp
• Use this pointer for cascading member
• function call
• pointThis.cpp

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Member function - friend

• Example
• Class Point
• friend Point setPoint(double, double, double)
• public
• Point(double 0.0, double 0.0,
• double 0.0)
• double getX() const return x // constant
  function
• private
• double x, y, z

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Member function friend (Cont.)

• Example (Cont.)
• Point setPoint(Point p,
• double sx, double sy, double sz)
• p.x sx
• p.y sy
• p.z sz
• return p

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Member function friend function Example

• Using class a 3D Point class
• pointFriend.cpp

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Member function - static

• Example
• Class Point
• friend Point setPoint(double, double, double)
• public
• Point(double 0.0, double 0.0,
• double 0.0)
• // static function to access static member data
• static int howmany ()
• private
• double x, y, z
• static int pointCount

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Member function static (Cont.)

• Example (Cont.)
• // initialize static member data
• int PointpointCount0
• // constructor
• PointPoint(double sx, double sy, double sz)
• // member initializer assign sx to x, sy to y
  and sz to z
• x(sx), y(sy), z(sz)
• pointCount

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Member function static (Cont.)

• Example (Cont.)
• // static function definition
• int Pointhowmany()
• return pointCount
• // main function
• int main()
• coutltlt "Total number of points created
  "ltltPointhowmany()ltltendl

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Member function static function Example

• Using class a 3D Point class
• pointStatic.cpp

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Operator Overloading

• Example
• Class Point
• friend istream
• operatorgtgt (istream , Point )
• public
• Point(double 0.0, double 0.0,
• double 0.0)
• private
• double x, y, z

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Operator Overloading (Cont.)

• Example (Cont.) // input form (m,n,r)
• istream operatorgtgt (istream input, Point p)
• input.ignore()
• input gtgt p.x
• input.ignore()
• input gtgt p.y
• input.ignore()
• input gtgt p.z
• input.ignore(5,'\n')
• return input

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Operator Overloading (Cont.)

• Example (Cont.)
• int main()
• Point p, q
• p.output()
• coutltlt"Please enter in 2 points in the form
  (m,n,r),
• ltlt e.g. (1.2,3.45,67.891)"
• cin gtgt p gtgt q
• p.output()
• q.output()
• cout ltlt '\n'

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Operator Overloading (Cont.) Example

• Using class a 3D Point class
• overload.cpp

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Template Function

• Form
• template ltclass T1, class T2gt
• returntype functionname (T1 var1 , T2 var2)

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Template Function (Cont.)

• Example template function for swap
• template ltclass Tgt
• void Bubbleswap(T x , T y)
• T tmp
• tmp x
• x y
• y tmp

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Template Function (Cont.)

• bubbleclass_template.cpp
• bubble_data.txt

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Class template

• Form
• template ltclass Tgt
• class classname
• public
• classname()
• returntype memberfunction (T var1, )
• T memberfunction (T var1, )
• classname()
• private
• T var3
• int var4,

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Class template (Cont.)

• Form (Cont.)
• template ltclass Tgt
• classnameltTgtclassname ()

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Class template (Cont.)

• Example A Bubble sort class
• template ltclass Tgt
• class Bubble
• public
• Bubble()
• void PrintData()
• void sort()
• Bubble()
• private
• T studentMAX_CLASS_SIZE
• int numStudents
• void swap(T x , T y)

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Class template (Cont.)

• Example A Bubble sort class (Cont.)
• template ltclass Tgt
• BubbleltTgtBubble()
• numStudents0
• while (cingtgtstudentnumStudents)
• numStudents

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Class template (Cont.)

• Complete Example
• No template
• bubbleclass_string.cpp
• bubble_data.txt

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Class template (Cont.)

• Complete Example (Cont.)
• Use class template
• bubble_classtemplate1.cpp
• bubbleclasstemplate1_data.txt (string data)
• bubble_classtemplate2.cpp
• bubbleclasstemplate2_data.txt (int data)

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References

• Deitel Deitel C How to Program, 4th ed.,
• Chapter 15, 16 17, Prentice Hall