C++11 lambdas and sqlite3_exec

bool Database::Execute(std::string const& query, RowHandler handler)
{
  // Create a closure that matches the callback signature sqlite3_exec wants.
  // Handler param passed as user data, so cast that to the correct type and call it.
  // Explicitly setting return type as int isn't 100% necessary as it can be deduced
  // from return type of RowHandler.
  auto wrapper = [](void* userData, int columnCount, char **columnValues, char **columnNames) -> int
  {
    auto handler = reinterpret_cast<RowHandler*>(userData);
    return (*handler)(columnCount, columnValues, columnNames);
  };

  return sqlite3_exec(db, query.c_str(), wrapper, &handler, /* error handling can wait */ nullptr);
}