第 15 章補充 --- 樣板 (template)

第15章補充 --- 樣板(template) • 列表8-4 swaps.cpp：參考值與函數參數 • 列表8-9 funtemp.cpp：函數樣板(template) • 列表8-10 twotemps.cpp：多載樣板 • 類別樣板(class template) – Stack<T> • 標準C++程式庫(Standard C++ Library) • complex<T> 範例程式 • 標準樣板程式庫(Standard Template Library, STL) • STL: stack<T> 範例程式 • 程式設計練習(一) • 程式設計練習(二)

列表 8-4 swaps.cpp：參考值與函數參數(1/3) #include <iostream.h> void swapr(int & a, int & b);// a, b are aliases for ints void swapp(int * p, int * q);// p, q are addresses of ints void swapv(int a, int b); // a, b are new variables int main(void) { int wallet1 = 300; int wallet2 = 350; cout << "wallet1 = $" << wallet1; cout << " wallet2 = $" << wallet2 << "\n"; cout << "Using references to swap contents:\n"; swapr(wallet1, wallet2); // pass variables cout << "wallet1 = $" << wallet1; cout << " wallet2 = $" << wallet2 << "\n"; cout << "Using pointers to swap contents:\n"; swapp(&wallet1, &wallet2);// pass addresses of variables cout << "wallet1 = $" << wallet1; cout << " wallet2 = $" << wallet2 << "\n";

列表 8-4 swaps.cpp：參考值與函數參數(2/3) cout << "Trying to use passing by value:\n"; swapv(wallet1, wallet2); // pass values of variables cout << "wallet1 = $" << wallet1; cout << " wallet2 = $" << wallet2 << "\n"; return 0; } void swapr(int & a, int & b) { // use references (參考值) int temp; temp = a; // use a, b for values of variables a = b; b = temp; } void swapp(int * p, int * q) { // use pointers (指標) int temp; temp = *p; // use *p, *q for values of variables *p = *q; *q = temp; }

列表 8-4 swaps.cpp：參考值與函數參數(3/3) void swapv(int a, int b) // try using values (數值) { int temp; temp = a; // use a, b for values of variables a = b; b = temp; } • wallet1 = $300 wallet2 = $350 • Using references to swap contents: • wallet1 = $350 wallet2 = $300 • Using pointers to swap contents: • wallet1 = $300 wallet2 = $350 • Trying to use passing by value: • wallet1 = $300 wallet2 = $350

列表8-9 funtemp.cpp：函數樣板(template) (1/2) #include <iostream.h> template <class Any> // function template prototype void swap(Any &a, Any &b); int main(void) { int i = 10, j = 20; cout << "i, j = " << i << ", " << j << ".\n"; cout << "Using compiler-generated int swapper:\n"; swap(i,j); // generates void swap(int &, int &) cout << "Now i, j = " << i << ", " << j << ".\n"; double x = 24.5, y = 81.7; cout << "x, y = " << x << ", " << y << ".\n"; cout << "Using compiler-generated double swapper:\n"; swap(x,y); //generates void swap(double&, double&) cout << "Now x, y = " << x << ", " << y << ".\n"; return 0; }

列表8-9 funtemp.cpp：函數樣板(template) (2/2) // function prototype definition template <class Any> void swap(Any &a, Any &b) { Any temp; temp = a; a = b; b = temp; }; • i, j = 10, 20. • Using compiler-generated int swapper: • Now i, j = 20, 10. • x, y = 24.5, 81.7. • Using compiler-generated double swapper: • Now x, y = 81.7, 24.5.

類別樣板(class template) – Stack<T> (1/3) • 堆疊(Stack)類別 -- ch13_ex2.cpp class Stack{ public: Stack(int size=10); ~Stack(){ delete [] Stk;}; Stack& operator<<(int item); Stack& operator>>(int &item); int IsEmpty() { return (top==-1); } private: int top; int StackSize; int *Stk; }; • 如何能存放不同的資料型態?

類別樣板(class template) – Stack<T> (2/3) #include <iostream.h> template<typename T> class Stack{ public: Stack(int size=10); ~Stack(){ delete [] Stk;}; Stack& operator<<(T item); Stack& operator>>(T &item); int IsEmpty() { return (top==-1); } private: int top; int StackSize; T *Stk; }; template<typename T> Stack<T>::Stack(int size) { Stk = new T [size]; StackSize = size; top = -1; }

類別樣板(class template) – Stack<T> (3/3) template<typename T> Stack<T>& Stack<T>::operator<<(T item) { top++; Stk[top] = item; return *this; } template<typename T> Stack<T>& Stack<T>::operator>>(T &item) { item = Stk[top]; top--; return *this; } main() { float item; Stack<float> s(10); s << 1.1; s << 2.2; s << 3.3; while(!s.IsEmpty()) { s >> item; cout << item << endl; } }

Standard C++ Library • 參考資料: Borland C++ Builder/Help/Standard C++ Library • The Standard C++ Library is a large and comprehensive collection of classes and functions for fine-grained, low-level programming. Within this library, you will find the following components: • The large set of data structures and algorithms formerly known as the Standard Template Library (STL) • An iostream facility • A locale facility • A templatized string class • A templatized complex class for representing complex numbers • A valarray class optimized for handling numeric arrays • A uniform framework for describing the execution environment, using a template class named numeric_limits and specializations for each fundamental datatype • Memory management features • Extensive support for national character sets • Exception handling features

complex<T> 範例程式 #include <complex> #include <iostream> using namespace std; main() { complex<double> x(1.0, 2.0); cout << x + x << x * x; }

STL: Container classes (容器類別) • Container types provided by the Standard C++ Library • vector Random access to elements, efficient insertion at end • vector<bool> Specialization of vector optimized for bool • list Efficient insertion and removal throughout • deque Random access, efficient insertion at front or back • set Elements maintained in order, efficient test for inclusion, insertion, and removal • multiset Set with repeated copies • bitset Bit container templated on size rather than contained type • map Access to values via keys, efficient insertion and removal • multimap Map permitting duplicate keys • string Character container enhanced for string operations • Container adaptors of the Standard C++ Library • stack Insertions and removals only from top • queue Insertions at back, removals from front • priority queue Efficient access and removal of largest values

STL: stack<T> • As a data abstraction, a stack is traditionally defined as any object that implements the operations defined in the following table: • Function Implemented operation • empty() Returns true if the collection is empty • size() Returns number of elements in collection • top() Returns (but does not remove) the topmost element in the stack • push(newElement) Pushes a new element onto the stack • pop() Removes (but does not return) the topmost element from the stack • Programs that use the stack data abstraction should include the file stack: • # include <stack>

STL: stack<T> 範例程式 #include <stack> #include <iostream> using namespace std; main() { stack<int> s; int item; s.push(1); s.push(2); s.push(3); while(!s.empty()) { item = s.top(); s.pop(); cout << item << endl; } }

程式設計練習(一) • 撰寫一個函數樣板max，使用兩個引數，傳回引數較大者。分別測試引數型態為int及double。 • 撰寫一個函數樣板iquote，以括上雙引號顯示引數。分別測試引數型態為int, double, 及字串.

程式設計練習(二) • 修改第十三章程式設計練習一(ch13_ex.cpp)的complex類別, 使其成為類別樣板, 能使用Complex<float>, Complex<double>, Complex<long double>等資料型態. • 提示: 類別樣板宣告 template <typename T> class Complex{ friend ostream& operator<<(ostream &out, Complex c) { out << "(" << c.real << "," << c.imag << "i)"; return out; } public: Complex(T r=0.0, T i=0.0){ real = r; imag = i;}; Complex operator+(Complex); //addition Complex operator-(Complex); //subtraction private: double real; double imag; };

第 15 章補充 --- 樣板 (template)