Semantic actions plus a specific node for grouping (parentheses) makes handling your examples easy (e.g. for your a < b < c example, you just need to be able to

Semantic actions plus a specific node for grouping (parentheses) makes handling your examples easy (e.g. for your a < b < c example, you just need to be able to distinguish ot from the grouped expression. You can do it by adding various flags to change the parser behavior too, but that certainly easily turns into a mess.