c++ - Can't invert operators order -

I have written a class on C ++ in my class and I override the plus operator.

This prototype is:

 WAR operator + (CONSTORE and var);   
 Why does the IDE tell me that this is correct:  
  one = 3; A + 5; // True   
 But is not it?  
  one = 3; 5 + A; // error   
 Do I have to add an object with this object to my object?  
 
 The reason for this is that operators are not symmetric as member functions, the operator you define , The purpose of that class should always be on the left side.  
 What do you want - you should work as an operator outside the classroom.  
  Var operator (Constable and Constant War amp);   
 And if you need to reach the private areas, then declare it as a friend festival.