is there some trick to have an epsilon_p as a root_node?
so id like this grammar to work:
= expression_1 >> *(root_node_d[epsilon_p] >> expression_2) //!!! doesnt work
= expression_2 >> *(
(root_node_d[ch_p('+')] >> expression_2) // works perfectly
(root_node_d[ch_p('-')] >> expression_2)
| inner_node_d['(' >> expression_0 >> ')']
unfortunately, there is no root node created for the rule expression_0.
so instead of building the abstract syntax tree for
"a b c d"
the tree is built as: