///////////////////////////////////////////////////////////////////////////
// convert.cpp - functions that convert type values to strings and back  //
// Exam4:Q5                                                              //
// Jim Fawcett, CSE687 - Object Oriented Design, Spring 2005             //
///////////////////////////////////////////////////////////////////////////

#include <sstream>
#include <iostream>
#include <stdexcept>

template <typename T>
std::string convert(const T& t)
{
  std::ostringstream os;
  os << t;
  if(!os.good())
  {
    std::string msg = "can't convert ";
    msg.append(typeid(T).name());
    throw std::invalid_argument(msg.c_str());
  }
  return os.str();
}

template <typename T>
T convert(const std::string& s)
{
  std::istringstream is(s);
  T t;
  is.seekg(std::ios::beg);
  is >> t;
  if(!is.good() && !is.eof())
  {
    std::string msg = "can't convert ";
    msg.append(s);
    throw std::invalid_argument(msg.c_str());
  }
  return t;
}

class foobar { } foo;

void main()
{
  std::cout << "\n  successfully converted " << 3.1415927 
            << " to \"" << convert(3.1415927).c_str() << "\"";
  std::cout << "\n  successfully converted " << "\"-17\"" 
            << " to " << convert<int>("-17");

  std::cout << "\n\n";

////////////////////////////////////////////////
//  fail to compile
//
//  std::string ex = convert(foo);
//  convert<foobar>("foobar");

  try
  {
    convert<int>("abc");  // throws exception
  }
  catch(exception& e)
  {
    std::cout << "\n  " << e.what() << "\n\n";
  }
}