CODEWITHSUNDEEP
c++structoperator-overloading
Rami Chasygov
Rami Chasygov

Reputation: 2784

Struct overloading with operator ==

I writing algorithm for converting roman to integer (Code below) and I got error 'too many parameters for this function', but I need two parameters for my comparison. Does someone know how fix my code?

#include <iostream>
using namespace std;

int main() {
  class Solution {
  private:
    struct symbol {
      char upperCase;
      char lowerCase;
      bool operator ==(char& a, symbol& b) { // ERROR: too many parametres for this function 
        return a == b.upperCase;
      };
    };
    const symbol one {'I', 'i'};
    // ...
    const symbol thousand {'M', 'm'};
  public:
    int romanToInt(string s) {
    // ...
    }
  };
  return 0;
}

Upvotes: 0

Views: 133

Answers (2)

Barmar
Barmar

Reputation: 780724

The left parameter of the operator is the automatic this object, you don't need to specify both parameters in the parameter list.

bool operator== (char& a) {
    return a == upperCase;
}

However, this only allows for symbol == char, not char == symbol. For the latter, you need a regular function, not a member function. You'll need to declare this as a friend of Solution so it can access the private symbol class.

  class Solution {
  private:
    struct symbol {
      char upperCase;
      char lowerCase;
      bool operator ==(const char& a) { // ERROR: too many parametres for this function 
        return a == upperCase;
      };
    };
    const symbol one {'I', 'i'};
    // ...
    const symbol thousand {'M', 'm'};
  public:
    int romanToInt(string s) {
    // ...
    }
    friend bool operator==(const char&, const symbol&)
  };

bool operator==(const char&a, const Solution::symbol& b) {
  return a == b.uppercase;
}

Upvotes: 3

p-a-o-l-o
p-a-o-l-o

Reputation: 10047

You'd be better have one overload for symbol objects, and another for char's:

  bool operator ==(symbol& b)
  {
    return (b.upperCase==upperCase);
  }
  bool operator ==(char& a)
  {
   return a == upperCase;
  }

In overloading the equal-to operator, the one and only argument is checked against the current instance (i.e. this).

Upvotes: 2

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