#include <iostream>
#include <boost/type_traits/is_base_of.hpp>
#include <boost/utility/enable_if.hpp>

using namespace std;

class Base {};

ostream& operator << ( ostream& o, const Base& b)
{
  o << "Base\n";
  return o;
}

class C : public Base {};
class D : public Base {};

template<typename T >
void operator + (const T& t , const Base& b )
{
  cout << "t+ " << t << "\n";
}

template<typename T >
void operator + (const Base& b, const T& t )
{
  cout << "+t " << t << "\n";
}

template<typename T >
void operator * (const T& t , const Base& b )
{
  cout << "t* " << t << "\n";
}

template<typename T >
typename boost::disable_if<boost::is_base_of<Base,T>, void>::type operator * (const Base& b, const T& t )
{
  cout << "*t " << t << "\n";
}

void test()
{
  C c;
  D d;
  c+3;
  5+d;
//  c+d;   // Compile time error
  c*3;
  5*d;
  c*d;
}

#include <boost/numeric/ublas/matrix_expression.hpp>
#include <boost/numeric/ublas/matrix.hpp>
#include <boost/numeric/ublas/io.hpp>

void test2()
{
  using namespace boost::numeric::ublas;
  matrix<double> A(3,3);
  matrix<double> B(3,3);

  A = B = zero_matrix<double>(3,3);

  A(0,0) = 3.0;
  B(0,0) = 3.0;

  cout << A*B << "\n";
}