inline std::string to_string( const container_type<F>& container, const char* delimeter = "; ") {
std::stringstream ss;
for(auto it = container.begin(); std::next(it)!=container.end(); ++it)
ss << *it << delimeter;
ss << container.back();
return ss.str();
}
node * create_node (value_type const & value
, priority_value_type priority
, node * left
, node * right)
{
_d.push_back(node(value, priority, left, right));
return & _d.back();
}