Hi all! can somebody help me with writing correct grammar rules for nested if statements? In my language, I am able to write constructions like this:
(IF CONDITION) some statements (IF CONDITION) some statements (ELSE IF CONDITION) some statements (ELSE IF CONDITION) some statements (ELSE IF CONDITION) some statements (ELSE) some statements (END) some statements (ELSE IF CONDITION) some statements (ELSE) some statements (END) I wrote lexer so left and right parenthesis are RULE_OPEN and RULE_CLOSE tokens, "IF" is IF token, "END" is END token, "ELSE" is ELSE token, "CONDITION" is CONDITION token. Assume that "some statements" may be anything that is allowed in my language (like in common programming language). It is important that it is possible to nest IF statements possibly infinitely. Hope this is clear, please let me know if I explained it badly. No matter how I am trying. I am always getting shift/reduce conflicts and parser is not accepting correct input. Even though, I have successfully wrote rules without else-if. When I add rules for else-if, code starts to be very complicated for me. Below is my sucessfull approach without else-if part (I listed only relevant rules): statements: statement statements: statements statement statement: code | data_out | rule rule: inline_if_statement | block_if_statement block_if_statement: RULE_OPEN IF CONDITION RULE_CLOSE statements RULE_OPEN END RULE_CLOSE block_if_statement: RULE_OPEN IF CONDITION RULE_CLOSE statements block_else_statement block_else_statement: RULE_OPEN ELSE RULE_CLOSE statements RULE_OPEN END RULE_CLOSE block_else_statement: empty empty : I think that this is very common problem in parsing and I hope that somebody here have already solved it :-) Thanks for helping! -- You received this message because you are subscribed to the Google Groups "ply-hack" group. To view this discussion on the web visit https://groups.google.com/d/msg/ply-hack/-/hlDkpSWm0SwJ. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/ply-hack?hl=en.
