// File "NestMain.cc, by KWR for CSE250, Spr'00.  Goes with NestPack/
// Illustrates nested "interfaces" in C++.
// All classes are put in the same file for simplicity.

#include <iostream>
#include <string>

class BST {
public:
   class Sortable {
   public:
      virtual bool lessThan(Sortable* rhs) const = 0;
      virtual bool lteq(Sortable* rhs) const = 0;
      virtual int compare(Sortable* rhs) const = 0;
      // returns -1 for <, 0 for ==, +1 for >
   };
};

class MySortableItem : public BST::Sortable {
   string key;
public:
   virtual bool lessThan(BST::Sortable* rhs) const {
      return key < ((MySortableItem*)rhs)->key;
   }
   virtual bool lteq(BST::Sortable* rhs) const {
      return key <= ((MySortableItem*)rhs)->key;
   }
   virtual int compare(BST::Sortable* rhs) const {
      return key.compare(((MySortableItem*)rhs)->key);
   }
   MySortableItem() {}
};

int main() {
   MySortableItem* ii = new MySortableItem();
   if (ii->compare(ii) != 0) {
      cout << "Something is weird!" << endl;
   } else {
      cout << "Compiles and runs OK." << endl;
   }
}

// Try running this forgetting to put in the *s after "Sortable", and
// see what error messages you get!  C++ will think you want a
// parameter of an abstract class by-value, which is impossible, but
// C++ will let you have a pointer to the abstract class as a parameter.

// LIKEWISE, try forgetting the *s after MySortableItem in the promotion 
// casts!  I fell into that one, out of familiarity with Java!