Question

I have encountered a list of errors when i was trying to execute this erase function to remove ‘2’ from my vector. I am not sure where is the problem. Help will be greatly appreciated!

STRUCT MyInt

struct MyInt
{
friend ostream &operator<<(ostream &printout, const MyInt &Qn)
{
   printout<< Qn.value << endl;
   return printout;
}

  int value;
  MyInt (int value) : value (value) {}
};

STRUCT MyStuff

struct MyStuff
{
  std::vector<MyInt> values;

  MyStuff () : values ()
  { }
};

MAIN

int main()
{
MyStuff mystuff1,mystuff2;

for (int x = 0; x < 5; ++x)
    {
        mystuff2.values.push_back (MyInt (x));
    }

vector<MyInt>::iterator VITER;
mystuff2.values.push_back(10);
mystuff2.values.push_back(7);

    //error points to the line below
mystuff2.values.erase(std::remove(mystuff2.values.begin(), mystuff2.values.end(), 2), mystuff2.values.end());

    return 0;

}

Error Messages

stl_algo.h: In Function ‘_OutputIterator std::remove_copy(_InputInputIterator, _InputIterator, const_Tp&) [with_InputIterator = __gnu_cxx:__normal_iterator > >, OutputIterator = __ gnu_cxx::__normal iterator > >, Tp = int]’

No match for operator==’

Erorr messages showed the partciular line violated practically stl_algo.h’s lines
Line 1267, 1190, 327, 1263, 208, 212, 216, 220, 228, 232, 236

Answer 1

You need to overload the == operator for class MyInt.

For example:

struct MyInt
{

friend ostream &operator<<(ostream &printout, const MyInt &Qn)
{
   printout<< Qn.value << endl;
   return printout;
}

// Overload the operator 
bool operator==(const MyInt& rhs) const
{
  return this->value == rhs.value;
}

  int value;
  MyInt (int value) : value (value) {}
};