returning a constructor?

This is a discussion on returning a constructor? within the C++ Programming forums, part of the General Programming Boards category; //hi i saw an example of the + operator overloaded and i see that that operator+ function returns a constructor ...

  1. #1
    Registered User
    Join Date
    Mar 2004
    Posts
    113

    returning a constructor?

    //hi i saw an example of the + operator overloaded and i see that that operator+ function returns a constructor what is the logic behind this?

    Code:
    Class MyClass{
          public:                  
               MyClass(int);//constructor     
                ...   
              //+ operator overloaded
              MyClass operator+(const MyClass &objetc)const
             {
                 //how this can work and why?
                  return MyClass(localData + object.localData)
             }
              ...
    };
    
    int main()
    {
         MyClass n1;
         MyClass n2(20);
         Mclass n3(6);
             
         n1 = n2+n3;
         return 0;
    }
    thanks for any help

  2. #2
    Registered User
    Join Date
    Mar 2002
    Posts
    1,595
    It's a form of optimization. In the code you have listed you can return anything that resolves to a MyClass object. Clearly, the MyClass constructor will return a MyClass object which can then act as the return object for + operator. It's sort of like using isalpha() in the following syntax:
    Code:
    char myString[] = "hello world";
    char ch;
    for(int i = 0; i < strlen(myString); ++i)
    {
       if(isalpha(ch))
    	 cout << "element " << i << " of myString is a letter" << endl;
       else
    	 cout << "element " << i << " of myString isn't a letter" << endl;
    }
    here, isalpha() returns a value that can be interpretted as true or false, which is what if() is looking for, so it works just fine.

  3. #3
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    Mar 2004
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    113
    good ,
    thanks

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