A simple expression is reported to be recursive in parser combinators

Question

Guess what is the result of this compilation?

import scala.util.parsing.combinator._

object ExprParser extends JavaTokenParsers {
    lazy val literal = int  
    lazy val int = rep("0")
}

The compiler says it intis recursive and requests its type . My experiment says that the core of recursion is hidden in the literal declaration! Delete it and you will see that the recursion is gone!

Answer 1

It is relevant here that JavaTokenParsersdefines something called literal.

And rep("0")actually rep(literal("0"))( literal- this is an implicit conversion from Stringto Parser[String]).

literal JavaTokenParsers , - . , , , - int literal.

, :

object ExprParser extends JavaTokenParsers {
  lazy val literal: Parser[List[String]] = int 
  lazy val int: Parser[List[String]] = rep("0")
}

.

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