/////////////////////////////////////////////////////////////////
//  ParamsDefaulted.cpp - demonstrate that virtual functions and
//                        default parameters don't mix.
//
//  Default parameters are applied statically, so you get the
//  default of the type of reference, not the type of object.
//
//  Jim Fawcett, CSE687 - Object Oriented Design, Spring 2003
/////////////////////////////////////////////////////////////////

#include <iostream>
#include <iomanip>
#include <string>
using namespace std;

///////////////////////////////////////////////////////////
//  base::defaults function call will be polymorphic
//  - Application of default parameter is static
//
class base
{
public:
  virtual ~base() {}
  virtual void defaults(int i=12);
  virtual base& id();
};

inline base& base::id()
{
  cout << endl << setw(30) << "  base object invoking:";
  return *this;
}

inline void base::defaults(int i)
{
  cout << setw(30) << "  base::defaults(int i):" << "i = " << i;
}

//
///////////////////////////////////////////////////////////
//  derived1::defaults function call will be polymorphic
//  - Application of default parameter is static
//
class derived : public base
{
public:
  virtual void defaults(int i=10);
  derived& id();
};

inline derived& derived::id()
{
  cout << endl << setw(30) << "  derived object invoking:";
  return *this;
}

inline void derived::defaults(int i)
{
  cout << setw(30) << "  derived::defaults(int i):" << "i = " << i;
}

//
const int UPPER = true;
template <char ch>
string title(const string &t,bool upper=false)
{
  string underline(t.length()+2,ch);
  string temp;
  if(upper)
    temp = string("\n ") + underline + string("\n  ");
  else
    temp = string("\n  ");
  return temp + t + string("\n ") + underline;
}

int main()
{
  cout << 
    title<'='>("Problems Mixing Virtual Functions and Default Parameters");

  cout.setf(ios::left,ios::adjustfield);
  base b;
  b.id().defaults();

  derived d;
  d.id().defaults();

  base& polyRef = d;
  polyRef.id().defaults();  // defaults are not polymorphic

  cout << endl << 
    "\n  We get one behavior if we use derived object: default to 10";
  cout << 
    "\n  Different behavior using base ref to derived object: default to 12";
  cout << endl <<
    title<'='>("Message: don't give virtual functions default parameters",UPPER);
  
  cout << "\n\n";
}

///////////////////////////////////////////////////////////////
//  The Message:
//    Don't use default parameters with virtual functions
//