量化交易之C++篇 - 函数模板的基本用法

// 函数模板的基本用法
#include <iostream>

using namespace std;

void swapInt(int& a, int& b) {

  int temp = a;
  a = b;
  b = temp;
}

void test01() {

  int a = 1;
  int b = 2;

  cout << "a: " << a << "     b: " << b << endl;
  swapInt(a, b);
  cout << "a: " << a << "     b: " << b << endl;
}

void swapDouble(double& a, double& b) {

  double temp = a;
  a = b;
  b = temp;
}

void test02() {

  double a = 1;
  double b = 2;

  cout << "a: " << a << "     b: " << b << endl;
  swapDouble(a, b);
  cout << "a: " << a << "     b: " << b << endl;

}

// 类型参数化 泛型编程 - 模板技术
template<class T> // 告诉编译器 下面如果出现T 不要报错, T是一个通用的类型
void mySwap(T& a, T& b) {
  T temp = a;
  a = b;
  b = temp;
}

void test03() {

  int a = 10;
  int b = 20;

  double c = 30;
  double d = 40;

  char e = 'e';
  char f = 'f';

  cout << "a: " << a << "     b: " << b << endl;
  mySwap(a, b); // 自动类型推导
  cout << "a: " << a << "     b: " << b << endl;

  cout << "c: " << c << "     d: " << d << endl;
  mySwap(c, d);
  cout << "c: " << c << "     d: " << d << endl;

  cout << "e: " << e << "     f: " << f << endl;
  mySwap(e, f);
  cout << "e: " << e << "     f: " << f << endl;
    
  cout << "a: " << a << "     b: " << b << endl;
  mySwap<int>(a, b); // 显示指定类型
  cout << "a: " << a << "     b: " << b << endl;
}

int main() {

  //test01();

  //test02();

  test03();

  return EXIT_SUCCESS;
}

// 利用模板实现char 和 int 的数组排序
#include <iostream>

using namespace std;

template<class T>
void mySwap(T& a, T& b) {
  T temp = a;
  a = b;
  b = temp;
}

template<class T>
void mySort(T arr[], int len) {

  for (int i = 0; i < len; i++) {
    int max = i;
    for (int j = i + 1; j < len; j++) {
      if (arr[max] > arr[j]) {
        max = j;
      }
    }
    if (max != i) {
      mySwap(arr[max], arr[i]); // 交换数据
    }
  }
}

template<class T>
void printArray(T arr[], int len) {
  for (int i = 0; i < len; i++) {
    cout << arr[i] << "  ";
  }
  cout << endl;
}

void test01() {

  char charArray[] = "helloworld";
  int len = strlen(charArray);

  mySort(charArray, len);

  printArray(charArray, len);
}

int main() {

  test01();

  return EXIT_SUCCESS;
}

// 模板的局限性以及解决
#include <iostream>
#include <string>

using namespace std;

class Person {

public:
  Person(string name, int age) {
    this->name = name;
    this->age = age;
  }

  string name;
  int age;
};

template<class T>
bool myCompare(T &a, T &b) {
  return (a == b);
}

void test01() {
  int a = 10;
  int b = 20;

  int result = myCompare(a, b);

  cout << "result = " << result << endl;
}

// 具体化自定义数据类型
template<> bool myCompare<Person>(Person& personA, Person& personB) {
  return (personA.age == personB.age);
}

void test02() {
  Person person1("roger", 19);
  Person person2("reiri", 19);

  int resultPerson = myCompare(person1, person2);
  cout << "resultPerson:" << resultPerson << endl;
}

int main() {

  //test01();

  test02();

  return EXIT_SUCCESS;
}

// 类模板的基本使用
#include <iostream>
#include <string>

using namespace std;

template<class NameType, class AgeType>
class Person {

public:
  Person(NameType name, AgeType age) {
    this->name = name;
    this->age = age;
  }

  void showInfomation() {
    cout << "name: " << this->name << "  age: " << this->age << endl;
  }

  NameType name;
  AgeType age;
};

void test01() {

  Person<string, int> person("kurohige", 45);

  person.showInfomation();
}

// 1. 指定传入类型
void doWork2(Person<string, int>& person) {

  person.showInfomation();
}

void test02() {

  Person<string, int> person("akagami", 40);

  doWork2(person);
}

// 2. 参数模板化
template<class T1, class T2>
void doWork3(Person<T1, T2>& person) {

  // 查看类型
  cout << "type T1: " << typeid(T1).name() << endl;
  cout << "type T2: " << typeid(T2).name() << endl;

  person.showInfomation();
}

void test03() {
  Person<string, int> person("big mom", 55);

  doWork3(person);
}

// 3. 整体模板化
template<class PersonType>
void doWork04(PersonType& person) {

  cout << "PersonType: " << typeid(PersonType).name() << endl;

  person.showInfomation();
}


void test04() {
  Person<string, int> person("gai do", 56);
  doWork04(person);
}

int main() {

  //test01();

  //test02();

  //test03();

  test04();

  return EXIT_SUCCESS;
}

// 类模板的继承问题
#include <iostream>
#include <string>

using namespace std;

template<class T> 
class Base {

public:
  T a;

};

// child 继承与 base 必须告诉base中的T的类型, 否则T无法分配内存
class Child : public Base<int> {

};

template<class T1, class T2>
class Child2 : public Base<T2> {

public:

  Child2() {
    cout << typeid(T1).name() << endl;
    cout << typeid(T2).name() << endl;
  }

  T1 b;
};

void test01() {
  Child2<int, double> child;
}

int main() {

  test01();

  return EXIT_SUCCESS;
}

// 类模板类外实现成员函数
#include <iostream>
#include <string>

using namespace std;

template<class T1, class T2>
class Person {

public:
  Person(T1 name, T2 age);

  void showInfomation();

  T1 name;
  T2 age;
};

template <class T1, class T2>
Person<T1, T2>::Person(T1 name, T2 age) {

  this->name = name;
  this->age = age;
}

template <class T1, class T2>
void Person<T1, T2>::showInfomation() {

  cout << "name: " << this->name << "   age: " << this->age;
}

int main() {

  Person<string, int> person("roger", 19);

  person.showInfomation();

  return EXIT_SUCCESS;
}

// Person.hpp
#pragma once

#include <iostream>
#include <string>

using namespace std;

template<class T1, class T2>
class Person {

public:
  Person(T1 name, T2 age);

  void showInfomation();

  T1 name;
  T2 age;
};

template <class T1, class T2>
Person<T1, T2>::Person(T1 name, T2 age) {

  this->name = name;
  this->age = age;
}

template <class T1, class T2>
void Person<T1, T2>::showInfomation() {

  cout << "name: " << this->name << "   age: " << this->age;
}

// 类模板与友元函数 - 类外实现
#include <iostream>
#include <string>

#include "Person.hpp" // 模板不要做份文件编写, 写入一个类中即可, 类内进行声明和实现, 最后把后缀名改为 .hpp 约定俗成

using namespace std;

void test01() {
  Person<string, int> person("roger", 19);

  person.showInfomation();
}

int main() {

  test01();

  return EXIT_SUCCESS;
}

// 类模板与友元函数 - 类内实现
#include <iostream>

using namespace std;

template<class T1, class T2>
class Person {
  // 友元函数类内实现
  friend void printPersonInside(Person<T1, T2>& person) {
    cout << "T1: " << person.name << "  T2: " << person.age << endl;
  }

  template<class T1, class T2>
  friend void printPersonOutSide(Person<T1, T2>& person); // 普通函数

public:

  Person(T1 name, T2 age) {
    this->name = name;
    this->age = age;
  }

private:
  T1 name;
  T2 age;

};

// 类外实现 类模板的友元函数
template<class T1, class T2>
void printPersonOutSide(Person<T1, T2>& person) {
  cout << "outside T1: " << person.name << "  inside T2: " << person.age << endl;
}

void test01() {

  Person<string, int> person("maruko", 26);
  printPersonInside(person);
}

void test02() {
  Person<string, int> person("maruko", 26);
  printPersonOutSide(person);
}

int main() {

  //test01();

  test02();

  return EXIT_SUCCESS;
}

// MyArray.hpp
#pragma once

#include <iostream>

using namespace std;

template<class T>
class MyArray {

public:
  explicit MyArray(int capacity) { // 防止隐式类型转换: 防止 MyArray array = 10; 写法
    this->capacity = capacity;
    this->size = 0;
    this->pAddress = new T[this->capacity];
  }

  MyArray(const MyArray& array) {
    this->capacity = array.capacity;
    this->size = array.size;
    this->pAddress = new T[this->capacity];

    for (int i = 0; i < this->size; i++) {
      this->pAddress[i] = array[i];
    }
  }

  // 赋值操作符= 重载
  MyArray& operator=(const MyArray& array) {
    if (this->pAddress != NULL) {
      delete[] this->pAddress;
      this->pAddress = NULL;
    }

    this->capacity = array.capacity;
    this->size = array.size;
    this->pAddress = new T[this->size];
    for (int i = 0; i < this->size; i++) {
      this->pAddress[i] = array[i];
    }
  }

  T& operator[](int index) {
    return this->pAddress[index];
  }

  int getSIze() {
    return this->size;
  }

  int getCapacity() {
    return this->capacity;
  }

  void pushBack(T value) {
    this->pAddress[this->size] = value;
    this->size++;
  }

  void printArray() {
    for (int i = 0; i < this->size; i++) {
      cout << "array[" << i << "]: " << this->pAddress[i] << endl;
    }
  }


  ~MyArray() {
    if (this->pAddress != NULL) {
      delete[] this->pAddress;
      this->pAddress = NULL;
    }
  }

private:
  T* pAddress; // 指向堆区内存
  int capacity;
  int size;
};

// 类模板的应用 - 数组类封装
#include <iostream>
#include "MyArray.hpp"

using namespace std;

void test01() {

  MyArray<int> array(10);
  for (int i = 0; i < 10; i++) {
    array.pushBack(i + 1);
  }

  array.printArray();
}

int main() {

  test01();

  return EXIT_SUCCESS;
}