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Object-Oriented Programming -- Using C++

Object-Oriented Programming -- Using C++. Andres, Wen-Yuan Liao Department of Computer Science and Engineering De Lin Institute of Technology andres@dlit.edu.tw http://cse.dlit.edu.tw/~andres. Chapter 11 - Templates.

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Object-Oriented Programming -- Using C++

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  1. Object-Oriented Programming-- Using C++ Andres, Wen-Yuan Liao Department of Computer Science and Engineering De Lin Institute of Technology andres@dlit.edu.tw http://cse.dlit.edu.tw/~andres

  2. Chapter 11 - Templates Outline11.1 Introduction11.2 Function Templates11.3 Overloading Function Templates11.4 Class Templates11.5 Class Templates and Nontype Parameters11.6 Templates and Inheritance11.7 Templates and Friends11.8 Templates and static Members

  3. 11.1 Introduction • Templates • Function templates • Specify entire range of related (overloaded) functions with a single code segment • Function-template specializations • Class templates • Specify entire range of related classes with a single code segment • Class-template specializations

  4. 11.2 Function Templates • Overloaded functions • Similar operations • Different types of data • Function templates • Identical operations • Different types of data • Single function template • Compiler generates separate object-code functions • Type checking

  5. 11.2 Function Templates (3.21) • Example template < class T > // or template< typename T > T square( T value1 ) { return value1 * value1; } • T is a formal type, used as parameter type • Above function returns variable of same type as parameter • In function call, T replaced by real type • If int, all T's become ints int square(int value1 ) { return value1 * value1; } • If double, all T's become doubles double square(double value1 ) { return value1 * value1; }

  6. 1 // Fig. 3.27: fig03_27.cpp 10 template < class T > 11 T maximum( T value1, T value2, T value3 ) { 13 T max = value1; 15 if ( value2 > max ) 16 max = value2; 18 if ( value3 > max ) 19 max = value3; 21 return max; 23 } 25 int main(){ 28 int int1, int2, int3; 31 cin >> int1 >> int2 >> int3; 34 cout << maximum( int1, int2, int3 ); 38 double double1, double2, double3; 41 cin >> double1 >> double2 >> double3; 44 cout << maximum( double1, double2, double3 ); 48 char char1, char2, char3; 51 cin >> char1 >> char2 >> char3; 54 cout << maximum( char1, char2, char3 ) 56 << endl; 58 return0; 60 } intmaximum(int value1, int value2, int value3 ) { intmax = value1; …… } doublemaximum(double value1, double value2, double value3 ) { doublemax = value1; …… } charmaximum(char value1, char value2, char value3 ) { charmax = value1; …… }

  7. Input three integer values: 1 2 3 The maximum integer value is: 3 Input three double values: 3.3 2.2 1.1 The maximum double value is: 3.3 Input three characters: A C B The maximum character value is: C

  8. 11.2 Function Templates • Function-template definitions • Keyword template • List formal type parameters in angle brackets (< and >) • Each parameter preceded by keyword class or typename • class and typename interchangeable template< class T > template< typename ElementType > template< class BorderType, class FillType > • Specify types of • Arguments to function • Return type of function • Variables within function

  9. 1 // Fig. 11.1: fig11_01.cpp 9 template< class T > 10 void printArray( const T *array, const int count ){ 12 for ( int i = 0; i < count; i++ ) 13 cout << array[ i ] << " "; 15 cout << endl; 17 } 19 int main(){ 21 const int aCount = 5; 22 const int bCount = 7; 23 const int cCount = 6; 25 int a[ aCount ] = { 1, 2, 3, 4, 5 }; 26 double b[ bCount ] = { 1.1, 2.2, 3.3, 4.4, 5.5, 6.6, 7.7 }; 27 char c[ cCount ] = "HELLO"; 29 cout << "Array a contains:" << endl; 32 printArray( a, aCount ); 34 cout << "Array b contains:" << endl; 37 printArray( b, bCount ); 39 cout << "Array c contains:" << endl; 42 printArray( c, cCount ); 44 return0; 46 } a[0] 1 b[0] c[0] 1.1 H a[1] 2 b[1] c[1] 2.2 E a[2] 3 b[2] c[2] 3.3 L a[3] 4 b[3] c[3] 4.4 L a[4] 5 b[4] c[4] 5.5 O b[5] c[5] 6.6 \0 b[6] 7.7 fig11_01.cpp(1 of 2) void printArray( constint *array, const int count ) { void printArray( constdouble *array, const int count ) { void printArray( constchar *array, const int count ) {

  10. Array a contains: 1 2 3 4 5 Array b contains: 1.1 2.2 3.3 4.4 5.5 6.6 7.7 Array c contains: H E L L O

  11. 11.3 Overloading Function Templates • Related function-template specializations • Same name • Compiler uses overloading resolution • Function template overloading template< class T > void printArray( const T *array, const int count ) • Function templates with same name • Different parameters template< class T > int printArray( T const * const array, int size, int lowSubscript, int highSubscript )

  12. 11.3 Overloading Function Templates • Function template overloading • Non-template functions with same name • Different function arguments void printArray( char const * const stringArray[], int size ) • Compiler performs matching process • Tries to find precise match of function name and argument types • If fails, function template • Generate function-template specialization with precise match

  13. 11.4 Class Templates • Stack • LIFO (last-in-first-out) structure • Class templates • Generic programming • Describe notion of stack generically • Instantiate type-specific version • Parameterized types • Require one or more type parameters • Customize “generic class” template to form class-template specialization

  14. 1 // Fig. 11.2: tstack1.h 6 template< class T > 7 class Stack { 9 public: 10 Stack( int = 10 ); 13 ~Stack() { 15 delete [] stackPtr; 17 } 19 bool push( const T& ); 20 bool pop( T& ); 23 bool isEmpty() const { 25 return top == -1; 27 } 30 bool isFull() const { 32 return top == size - 1; 34 } 36 private: 37 int size; // # of elements in the stack 38 int top; // location of the top element 39 T *stackPtr; // pointer to the stack 41 }; class Stack + Stack( int = 10 ); + ~Stack() + bool push( const T& ); + bool pop( T& ); + bool isEmpty() const + bool isFull() const • - int size; • int top; • T *stackPtr; T tstack1.h (1 of 4) [9] [8] [7] [6] [5] [4] [3] [2] [1] [0]

  15. 44 template< class T > 45 Stack< T >::Stack( int s ){ 47 size = s > 0 ? s : 10; 48 top = -1; // Stack initially empty 49 stackPtr = new T[ size ]; 51 } 55 template< class T > 56 bool Stack< T >::push( const T &pushValue ){ 58 if ( !isFull() ) { 59 stackPtr[ ++top ] = pushValue; 60 returntrue; 62 } 64 returnfalse; 66 } 70 template< class T > 71 bool Stack< T >::pop( T &popValue ){ 73 if ( !isEmpty() ) { 74 popValue = stackPtr[ top-- ]; // remove item from Stack 75 returntrue; 77 } 79 return false; 81 } class Stack + Stack( int = 10 ); + ~Stack() + bool push( const T& ); + bool pop( T& ); + bool isEmpty() const + bool isFull() const • - int size; • int top; • T *stackPtr; T [9] [8] [7] [6] [5] [4] [3] [2] [1] [0]

  16. 1 // Fig. 11.3: fig11_03.cpp 9 #include"tstack1.h" 11 int main(){ 13 Stack< double > doubleStack( 5 ); 14 double doubleValue = 1.1; 18 while ( doubleStack.push( doubleValue ) ) { 19 cout << doubleValue << ' '; 20 doubleValue += 1.1; 22 } 24 cout << "\nStack is full. Cannot push " << doubleValue 25 << "\n\nPopping elements from doubleStack\n"; 27 while ( doubleStack.pop( doubleValue ) ) 28 cout << doubleValue << ' '; 30 cout << "\nStack is empty. Cannot pop\n"; 32 Stack< int > intStack; 33 int intValue = 1; 34 cout << "\nPushing elements onto intStack\n"; 36 while ( intStack.push( intValue ) ) { 37 cout << intValue << ' '; 38 ++intValue; 40 } Stack doubleStack • - size = 5; • - top = -1; • double *stackPtr; 10 9 5.5 8 4.4 7 3.3 6 2.2 5 1.1 Stack intStack 4 • - size = 10; • - top = -1; • int *stackPtr; 3 2 1 [4] [3] [2] [1] [0] [9] [8] [7] [6] [5] [4] [3] [2] [1] [0]

  17. 42 cout << "\nStack is full. Cannot push " << intValue 43 << "\n\nPopping elements from intStack\n"; 45 while ( intStack.pop( intValue ) ) 46 cout << intValue << ' '; 48 cout << "\nStack is empty. Cannot pop\n"; 50 return0; 51 52 } fig11_03.cpp(3 of 3)fig11_03.cppoutput (1 of 1) Pushing elements onto doubleStack 1.1 2.2 3.3 4.4 5.5 Stack is full. Cannot push 6.6 Popping elements from doubleStack 5.5 4.4 3.3 2.2 1.1 Stack is empty. Cannot pop Pushing elements onto intStack 1 2 3 4 5 6 7 8 9 10 Stack is full. Cannot push 11 Popping elements from intStack 10 9 8 7 6 5 4 3 2 1 Stack is empty. Cannot pop

  18. 1 // Fig. 11.4: fig11_04.cpp 10 #include"tstack1.h" 13 template< class T > 14 void testStack( 15 Stack< T > &theStack, // reference to Stack< T > 16 T value, // initial value to push 17 T increment, // increment for subsequent values 18 const char *stackName ){ 20 cout << "\nPushing elements onto " << stackName << '\n'; 22 while ( theStack.push( value ) ) { 23 cout << value << ' '; 24 value += increment; 26 } 28 cout << "\nStack is full. Cannot push " << value 29 << "\n\nPopping elements from " << stackName << '\n'; 31 while ( theStack.pop( value ) ) 32 cout << value << ' '; 34 cout << "\nStack is empty. Cannot pop\n"; 36 } class Stack + Stack( int = 10 ); + ~Stack() + bool push( const T& ); + bool pop( T& ); + bool isEmpty() const + bool isFull() const • - int size; • int top; • T *stackPtr; T theStack

  19. 38 int main(){ 40 Stack< double > doubleStack( 5 ); 41 Stack< int > intStack; 43 testStack( doubleStack, 1.1, 1.1, "doubleStack" ); 44 testStack( intStack, 1, 1, "intStack" ); 46 return0; 48 } Stack doubleStack • - size = 5; • - top = -1; • double *stackPtr; 10 9 5.5 8 4.4 7 3.3 6 2.2 5 1.1 Stack intStack 4 • - size = 10; • - top = -1; • int *stackPtr; 3 2 1 theStack [4] [3] [2] [1] [0] Pushing elements onto doubleStack 1.1 2.2 3.3 4.4 5.5 Stack is full. Cannot push 6.6 Popping elements from doubleStack 5.5 4.4 3.3 2.2 1.1 Stack is empty. Cannot pop Pushing elements onto intStack 1 2 3 4 5 6 7 8 9 10 Stack is full. Cannot push 11 Popping elements from intStack 10 9 8 7 6 5 4 3 2 1 Stack is empty. Cannot pop void testStack( Stack< double > &theStack, double value, doubleincrement, const char *stackName ) [9] void testStack( Stack< int > &theStack, int value, intincrement, const char *stackName ) [8] [7] [6] [5] [4] theStack [3] [2] [1] [0]

  20. 11.5 Class Templates and Nontype Parameters • Class templates • Nontype parameters • Default arguments • Treated as consts • Example: template< class T, int elements > Stack< double, 100 > mostRecentSalesFigures; • Declares object of type Stack< double, 100> • Type parameter • Default type • Example: template< class T = string >

  21. T T T 11.6 Templates and Inheritance • Several ways of relating templates and inheritance • Class template derived from class-template specialization • Class template derived from non-template class • Class-template specialization derived from class-template specialization • Non-template class derived from class-template specialization <T> <T> <T>

  22. 11.7 Templates and Friends • Friendships between class template and • Global function • Member function of another class • Entire class

  23. 11.7 Templates and Friends template< class T > class X { friend void f1(); friend void f2( X< T > & ); friend void A::f4(); friend void C< T >::f5( X< T > & ); friend class Y; friend class Z<T>; };

  24. 11.7 Templates and Friends • friend functions • Inside definition of template< class T > class X • friend void f1(); • f1()friend of all class-template specializations • friend void f2( X< T > & ); • f2( X< float > & )friend of X< float > only, f2( X< double > & )friend of X< double > only, f2( X< int > & )friend of X< int > only, … • friend void A::f4(); • Member function f4 of class Afriend of all class-template specializations

  25. 11.7 Templates and Friends • friend functions • Inside definition of template< class T > class X • friend void C< T >::f5( X< T > & ); • Member function C<float>::f5( X< float> & )friend of class X<float> only • friendclasses • Inside definition of template< class T > class X • friend class Y; • Every member function of Y friend of every class-template specialization • friend class Z<T>; • class Z<float>friend of class-template specialization X<float>, etc.

  26. 11.8 Templates and static Members • Non-template class • static data members shared between all objects • Class-template specialization • Each has own copy of static data members • static variables initialized at file scope • Each has own copy of static member functions

  27. Programming Homework • 10.14 • 11.7 • Deadline: 12/15

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