void attach( expr_ptr const &a, std::deque<expression_type> &operator_deq, std::deque<expr_ptr> &children_deq )
{
for( size_t i = 0; i != a->num_children(); ++i ){
expression_type type_of_expr = a->get_children( i )->get_type();
if( type_of_expr == expression_type::Plus ){
operator_deq.push_back( type_of_expr );
attach( a->get_children( i ), operator_deq, children_deq );
} else {
children_deq.push_back( a->get_children( i ) );
}
}
}
expr_ptr build_rightmost_tree( expr_ptr const &a, expr_ptr &node, expression_type in )
{
expr_ptr right_tree = build_tree_for( in );
right_tree->set_children( 1, a );
right_tree.swap( node );
node->set_children( 0, right_tree );
return node->get_children( 1 );
}