C++ Primer Plus 学习笔记第十四章指针类型模板模板多功能型模板的具体化

柔光的暖阳◎ 2022-01-23 14:57 342阅读 0赞

程序示例

stcktp1.h

#ifndef STCKTP1_H_
    #define STCKTP1_H_
    
    template <class Type>
    class Stack
    {
      private:
        enum {SIZE = 10};
        int stacksize;
        Type * items;
        int top;
      public:
        explicit Stack(int ss = SIZE);
        Stack(const Stack & st);
        ~Stack() {delete [] items;}
        bool isempty() {return top == 0;}
        bool isfull() {return top == stacksize;}
        bool push(const Type & item);
        bool pop(Type & item);
        Stack & operator= (const Stack & st);
    };
    
    template <class Type>
    Stack<Type>::Stack(int ss) : stacksize(ss), top(0)
    {
      items = new Type [stacksize];
    }
    
    template <class Type>
    Stack<Type>::Stack (const Stack & st)
    {
      stacksize = st.stacksize;
      top = st.top;
      items = new Type [stacksize];
      for (int i = 0; i < top; i++)
        items[i] = st.items[i];
    }
    
    template<class Type>
    bool Stack<Type>::push(const Type & item)
    {
      if (top < stacksize)
      {
        items[top++] = item;
        return true;
      }
      else
        return false;
    }
    
    template<class Type>
    bool Stack<Type>::pop(Type & item)
    {
      if (top > 0)
      {
        item = items[--top];
        return true;
      }
      else
        return false;
    }
    
    template<class Type>
    Stack<Type> & Stack<Type>::operator=(const Stack<Type> & st)
    {
      if (this == &st)
        return *this;
      delete [] items;
      stacksize = st.stacksize;
      top = st.top;
      items = new Type [stacksize];
      for(int i = 0; i < top; i++)
        items[i] = st.items[i];
      return *this;
    }
    
    #endif

stkoptr1.cpp

#include <iostream>
    #include <cstdlib>
    #include <ctime>
    #include "stcktp1.h"
    
    const int Num = 10;
    int main()
    {
      std::srand(std::time(0));
      std::cout << "Please enter stack size: ";
      int stacksize;
      std::cin >> stacksize;
      Stack<const char *> st(stacksize);
    
      const char* in[Num] = {
        "1: Hank Gilgamesh", "2: Kiki Ishtar",
        "3: Betty Rocker", "4: Ian Flagranti",
        "7: Joy Almondo", "8: Xaverie Paprika",
        "9: Juan Morre", "10: Misha Mache"
      };
      const char* out[Num];
    
      int processed = 0;
      int nextin = 0;
      while (processed < Num)
      {
        if (st.isempty())
          st.push(in[nextin++]);
        else if(st.isfull())
          st.pop(out[processed++]);
        else if (std::rand() % 2 && nextin < Num)
          st.push(in[nextin++]);
        else
          st.pop(out[processed++]);
      }
      for (int i = 0; i < Num; i++)
        std::cout << out[i] << std::endl;
    
      std::cout << "Bye\n";
      return 0;
    }

![20190604131254323.png][]

表达式参数类模板：

![20190604131309235.png][]

程序示例：

arraytp.h

#ifndef ARRAYTP_H_
    #define ARRAYTP_H_
    
    #include <iostream>
    #include <cstdlib>
    
    template<class T, int n>
    class ArrayTP
    {
      private:
        T ar[n];
      public:
        ArrayTP() {};
        explicit ArrayTP(const T & v);
        virtual T & operator[] (int i);
        virtual T operator[] (int i) const;
    };
    
    template<class T, int n>
    ArrayTP<T, n>::ArrayTP(const T & v)
    {
      for (int i = 0; i < n; i++)
        ar[i] = v;
    }
    
    template<class T, int n>
    T & ArrayTP<T, n>::operator[](int i)
    {
      if (i < 0 || i >= n)
      {
        std::cerr << "Error in array limits: " << i
            << " is out of range\n";
        std::exit(EXIT_FAILURE);
      }
      return ar[i];
    }
    
    template <class T, int n>
    T ArrayTP<T, n>::operator[](int i) const
    {
      if (i < 0 || i >= n)
      {
        std::cerr << "Error in array limits: " << i
            << " is out of range\n";
        std::exit(EXIT_FAILURE);
      }
      return ar[i];
    }
    
    #endif

twod.cpp

#include <iostream>
    #include "arraytp.h"
    int main()
    {
      using std::cout;
      using std::endl;
      ArrayTP<int, 10> sums;
      ArrayTP<double, 10> aves;
      ArrayTP< ArrayTP<int, 5>, 10> twodee;
    
      int i, j;
      for (i = 0; i < 10; i++)
      {
        sums[i] = 0;
        for (j = 0; j < 5; j++)
        {
          twodee[i][j] = (i + 1) * (j + 1);
          sums[i] += twodee[i][j];
        }
        aves[i] = (double) sums[i] / 10;
      }
      for (i = 0; i < 10; i++)
      {
        for (j = 0; j < 5; j++)
        {
          cout.width(2);
          cout << twodee[i][j] << ' ';
        }
        cout << ": sum = ";
        cout.width(3);
        cout << sums[i] << ", average = " << aves[i] << endl;
      }
    
      cout << "Done.\n";
    
      return 0;
    }

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NvdWx3eWI_size_16_color_FFFFFF_t_70][]

运行结果：

![20190604131528860.png][]![20190604133618108.png][]

多类型模板参数

就是模板参数是多个class

程序示例pairs.cpp

#include <iostream>
    #include <string>
    
      using std::cout; 
      using std::cin;
      using std::endl;
      using std::string;
    
    template <class T1, class T2>
    class Pair
    {
      private:
        T1 a;
        T2 b;
      public:
        T1 & first();
        T2 & second();
        T1 first() const { return a;}
        T2 second() const { return b;}
        Pair(const T1 & aval, const T2 & bval) : a(aval), b(bval) {}
        Pair() {}
    };
    
    template<class T1, class T2>
    T1 & Pair<T1, T2>::first()
    {
    // 这个我是在测试调哪个first()
      cout << "1&";
      return a;
    }
    template<class T1, class T2>
    T2 & Pair<T1, T2>::second()
    {
      cout << "2&";
      return b;
    }
    
    int main()
    {
      using std::cout;
      using std::cin;
      using std::endl;
      using std::string;
      Pair<string, int> ratings[4] =
      {
        Pair<string, int> ("The Purpled Duck", 5),
        Pair<string, int> ("Jaquie's Frisco Al Fresco", 4),
        Pair<string, int> ("Cafe Souffle", 5),
        Pair<string, int> ("Bertie's Eats", 3)
      };
    
      int joints = sizeof(ratings) / sizeof (Pair<string, int>);
      cout << "Rating:\t Eatery\n";
      for (int i = 0; i < joints; i++)
        cout << ratings[i].second() << ":\t "
             << ratings[i].first() << endl;
    
      cout << "Oops! Revised rating:\n";
      ratings[3].first() = "Bertie's Fab Eats";
      ratings[3].second() = 6;
      cout << ratings[3].second() << ":\t "
           << ratings[3].first() << endl;
      return 0;
    }

类模板类型参数和非类型参数都可以指定默认值。 函数模板不支持类型参数带默认值。 但是非类型参数可以

以上都是模板隐式实例化

还有显示实例化

![20190604140350438.png][]

。。嗯。。。这有毛用？

然后是显示具体化

就是为特定具体类另外单独定义模板内容的

![20190604140557215.png][]

![20190604140603909.png][]

![20190604140612228.png][]

template <> class SortedArray<const char \*> 例子中是 SortedArray<const char char\*> 完全不知道为毛要多一个char

在使用char\* 类的时候就会调用该显示具体化的模板

部分具体化

template<class T1> Pair<T1, int> \{...\}

吧没有具体化的参数丢到前面的那个<>中去

C++调用模板的顺序：

具体化程度越高越优先调用。 有指针具体化的先调指针具体化版本。不然就用通用的转换。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NvdWx3eWI_size_16_color_FFFFFF_t_70 1][]

![20190604141409774.png][]

完结

[20190604131254323.png]: /images/20220123/93e2063337854cd2a394e120d170dda2.png
[20190604131309235.png]: /images/20220123/dc471b7bb59d4b84b3131816c54bc0e6.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NvdWx3eWI_size_16_color_FFFFFF_t_70]: /images/20220123/465236ae91054689aee65f128287d706.png
[20190604131528860.png]: https://img-blog.csdnimg.cn/20190604131528860.png
[20190604133618108.png]: /images/20220123/276bb3ea168b445daea2e396eabd7439.png
[20190604140350438.png]: /images/20220123/e14955d836e841619ed475eea6d5788c.png
[20190604140557215.png]: /images/20220123/a79f3f4db83e4d869397f7bf8bc665f0.png
[20190604140603909.png]: /images/20220123/e46934697e644c829f76dcffba376bf5.png
[20190604140612228.png]: /images/20220123/b60c73271f474d149f7afcf56be53488.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3NvdWx3eWI_size_16_color_FFFFFF_t_70 1]: /images/20220123/a10b4bc07cb54ab8a0d9937993a525a1.png
[20190604141409774.png]: /images/20220123/050a12fa3eca41f4a9055915f07772d0.png