小编ami*_*zle的帖子

任何人都可以解释之间的区别:

const char& operator[] const

和

char& operator[]

在C++中？是第二个复制字符串是真的吗？为什么？

我在C++中有以下代码:

#include <iostream> 

class Number 
{ 
public: 
    virtual void foo(){std::cout << "Number foo\n";};
    Number (){ std::cout << "Number ctor" << std::endl;} 
    virtual ~Number(){ std::cout << "Number dtor" << std::endl;} 
}; 


class Complex : public Number 
{ 
public:
    virtual void foo(){std::cout << "Complex foo\n";};
    Complex (double r=0, double i=0) : _r (r), _i (i)
    { std::cout << "Complex ctor" << std::endl; };
    virtual ~Complex(){ std::cout << "Complex dtor" << std::endl;}
private: 
    double _r,_i;
};


int main()
{
    Number *numArr = new …

我有以下C++代码:

#include <iostream>

template <class T>
void assign(T& t1, T& t2) {
   std::cout << "First method" << std::endl;
   t1 = t2;
}

template <class T>
void assign(T& t1, const T& t2) {
   std::cout << "Second method" << std::endl;
   t1 = t2;
}

class A {
   public:
      A(int a) : _a(a) {};
   private:
      int _a;
      friend A operator+(const A& l, const A& r);
};

A operator+(const A& l, const A& r) {
   return A(l._a + r._a);
}

int main() {
  A …