how to implement c++ table lookup?

[Speedo]

The cleanest option from a usage POV is probably going to be to make a little wrapper class around your map that lets you access it with operator(). You could then use the singleton pattern to prevent the map from being duplicated, and simply use the constructor of the wrapper class to initialize the map.

Would look something like:

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

class Table
{
  typedef std::map<std::pair<int, int>, int> TableMap;
  TableMap m_table;

  Table( )
  {
    m_table[std::make_pair(0, 0)] = 1;
    m_table[std::make_pair(0, 8)] = 3;
  }

  Table(Table&);
  Table& operator=(Table&);

public:
  static Table& GetSingleton( )
  {
    static Table instance;
    return instance;
  }

  int operator()(int x, int y) const
  {
    TableMap::const_iterator it = m_table.find(std::make_pair(x, y));

    if (it == m_table.end( ))
    {
      std::stringstream ss;
      ss << "Value (" << x << "," << y << ") not in table";
      throw std::out_of_range(ss.str( ));
    }

    return it->second;
  }
};

int main( )
{
  try
  {
    std::cout << Table::GetSingleton( )(0, 0) << std::endl;
    std::cout << Table::GetSingleton( )(0, 1) << std::endl;
  }
  catch (const std::exception& e)
  {
    std::cout << e.what( ) << std::endl;
  }

  return 0;
}