const，template，pointer，virtual

最新推荐文章于 2021-12-20 14:41:29 发布

gorunbu

最新推荐文章于 2021-12-20 14:41:29 发布

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分类专栏： c++ 文章标签： template

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本文详细解析了模板类中使用运算符重载时可能出现的问题，特别是与const结合使用时的注意事项，通过实例代码展示错误原因及解决方法。

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typdef 以及 typename 声明类型时候，需要注意与const 使用时的修饰作用。
//pointer operator, not allowed //error: invalid operands of types ‘int*’ and ‘int*’ to binary ‘operator+’【指针不能重载运算符】

#include <stdio.h>
#include <stdlib.h>

#include <iostream>
#include <string>

template <typename T>
class base
{

public:
    virtual void print(const T i)
    { printf("base:: i=%x, *i=%x\n",i,*i);}
};

class baseDerived:public base<int*>
{
public:
//  void print(const int* i)  //not override
//  { printf("baseDerived:: i=%x, *i=%x\n",i,*i);}

    void print(int* const i)
    { printf("baseDerived:: i=%x, *i=%x\n",i,*i);}
};

//pointer operator, not allowed //error: invalid operands of types 'int*' and 'int*' to binary 'operator+'
//int* operator +(int* p1,int* p2)
//{
//  return  int*( (unsigned long)p1 +(unsigned long)p2 );
//}

int main()
{
    base<int*>* b1=new baseDerived;
    baseDerived* d1=new baseDerived;
    int p=10;
    b1->print(&p);
    d1->print(&p); 

    base<int*>* b2=new base<int*>;
    b2->print(&p);

    delete b1;
    delete b2;
    delete d1;
}

template <typename T>
class base
{
    T data;
public:
    base(){};
    base(T num):data(num)
    {}
    virtual void print(const T i)
    { printf("base:: i=%x, *i=%x\n",i,1);} //*i
    virtual T operator +(T& other)
    { printf("base:: operator+ %x + %x\n",data,other); return data+other;}
};

class baseDerived1:public base<int>
{
    int data;
public:
    baseDerived1(){}
    baseDerived1(int num):data(num)
    {}
    int operator +(int& other)
    { printf("base:: operator+ %x + %x\n",data,other); return data+other;}

    void print(int* const i)
    { printf("baseDerived:: i=%x, *i=%x\n",i,*i);}
};
int main()
{

    base<int>* b11=new baseDerived1(1);
    baseDerived1* d11=new baseDerived1(2);
    int oa=5;
    printf("b11+5=%x\n",*b11+oa);
    printf("d11+5=%x\n",*d11+oa);

    base<int>* b12=new base<int>(5);
    printf("b12+5=%x\n",*b12+oa);

}