asturaphoenix / alchemy Goto Github PK

Current assertion:

It is less straightforward to get top-down parsing to handle rewrite rules since top-down parsers are guided by a map of productions to patterns. In the case of rewrite rules, these productions can potentially be expansions or dynamic, which would need to be matched against the pending production in a top-down parse. This is doable, but involves a potential inverse function/production analysis, or may turn into a hybrid top-down-bottom-up parse.

Actually, I think a rewrite can be performed top-down by backtracking to where the rewrite began. This may greatly simplify the parse algorithm if we can get it to reconsider all relevant decision branches when it does such a backtrack, and if we can get it to work with retroactive rules.

Also: keep reading http://dotat.at/tmp/gll.pdf