// Prog: statements_template.cpp
// prints the value of a variable 

#include<iostream>
#include<vector>
#include<cassert>

// base class for all statements
struct statement {
  virtual void execute () {};
};

// base class for all expressions
template <typename T>
struct expression {
  virtual T get_value () const {}
 };

template <typename T>
struct lvalue : public expression<T> {
   virtual void set_value (const T& v) {}
};

// variable with initial value
template<typename T>
struct variable: public lvalue<T> {
  T val;
  
  variable (const T& v)
    : val (v)
  {}

  T get_value () const
  {
    return val;
  }

  void set_value (const T& v)
  {
    val = v;
  }
};

// print the value of an expression
template<typename T>
struct print : public statement {
  expression<T>* exp;
  
  print (expression<T>* e)
    : exp (e)
  {}
  
  // POST: the value of *var is printed to std::cout
  void execute () 
  {
    std::cout << exp->get_value();
  }
  
};

int main()
{
  variable<int> s = 10; 
  print<int> output (&s);

  // execute statements
  output.execute(); 

  std::cout << std::endl;

  return 0;
}