I've tried
/* inside RegexParser class */
def exp : Parser[Exp] =
term~addop_chain ^^ {case l~ThenAdd(optype,r) => AritOp(l,optype,r)}
def addop_chain : Parser[Exp] =
("+"|"-")~term~addop_chain ^^ {case sym~term~ThenAdd(optype,r) => ThenAdd(sym, AritOp(term,optype,r)) } |
("+"|"-")~term ^^ {case sym~term => ThenAdd(sym, term)}
def term = /* right now, only int literal. code unrelevant */
/* Case classes for storing: */
case class ThenAdd(sym: String, r: Exp)
case class AritOp(l: Exp, sym: String, r: Exp)
Which works!, but is right-assoc (not left-assoc), e.g. 5+(3-2), which is not what I want.
What I want is something like:
5+3-2
should become
AritOp(AritOp(5,+,3), -, 2)
(left assoc) But this feels almost impossible without (proper?) left recursion. What can I do?
(constriant: I can't use rep, repsep, opt (I'm doing an assignment, so the grammer should be as BNF as possible (ie. not EBNF)))
