// Given a name of the form "table.function", retrieves a function
// from a set of nested tables. (There can be 0 or more "table"s in the name.)
// Pushes the named function to the stack on success, and nil on failure.
bool GetNestedFunction (lua_State * L, const char * sName, const bool bRaiseError)
  {
  // L: ...

  vector<string> v;
  StringToVector (sName, v, ".", true);

  // get the method from the end, leaving only table names in the vector
  string sMethod = v.back ();
  v.pop_back ();

  // run down the vector to get to the table containing the method.
  // Start with the globals table, _G.
  lua_pushvalue(L, LUA_GLOBALSINDEX); // L: ... _G
  string sTable = "_G";

  vector<string>::const_iterator iter = v.begin ();
  vector<string>::const_iterator end = v.end ();
  for (; iter != end; ++iter)
    {
    // L: ... parent
    if (!lua_istable (L, -1))
      break; // it's not a table, so we can't get the method we wanted

    // pull the child table out, and remove the parent
    lua_getfield (L, -1, iter->c_str ()); // L: ... parent, child
    lua_remove (L, -2); // L: ... child

    sTable = *iter;
    }
  // L: ... table

  // make sure the last thing was a table
  if (lua_istable (L, -1))
    {
    // get the method and remove the table
    lua_getfield (L, -1, sMethod.c_str ()); // L: ... table, function
    lua_remove (L, -2); // L: ... function

    // make sure we have a function
    if (lua_isfunction (L, -1))
      return true; // L: ... function
    else
      sTable = sMethod; // for the error message at the bottom
    }
  // ... unknown

  if (bRaiseError)
    ::UMessageBox (TFormat ("Cannot find the function '%s' - item '%s' is %s",
                            sMethod, 
                            sTable.c_str (),
                            luaL_typename (L, -1)), 
                   MB_ICONEXCLAMATION);

  lua_pop (L, 1); // L: ...
  lua_pushnil (L); // L: ... nil
  return false; // L: ... nil
  }

local func, err = get_nested_function("foo.bar")
if func == nil then
  error(err)
end