Scala pass List of Expressions and another Expression as one list to Constructor

Question

I'm currently writing a Parser which extends JavaTokenParsers in Scala which should amongst other things parse following Grammar:

list = "[" [ { expr "," } expr ] "]"

My Parser Class:

class ExpParser extends JavaTokenParsers {

  def expr: Parser[Expression] = int | list | bool | id

  [...]    
  private def list: Parser[Liste] = "[" ~> repsep(expr, ",") ~ expr <~ "]"  ^^ {
    case el ~ e => Liste(List(el, e))
  }       // error

  [..]
}

object ParseProgram extends ExpParser {
  def parse(s: String): ParseResult[Expression] = {
    parseAll(expr, s)
  }
}

My Case Class:

sealed trait Expression
[...]
case class Liste(l: List[Expression]) extends Expression
[...]

I tried to create a new List and pass it to the Liste Constructor but i get following error message:

Type mismatch, expected: List[Expression], actual: List[Object]

So how can i pass the list of Expressions which i get from repsep(expr, ",") and the expression which i get from ~ expr as one list to the Liste Constructor?

Answer 1

repsep(expr, ",") gives you a Parser[List[Expression]] and isn't that enough?

private def list: Parser[Liste] = "[" ~> repsep(expr, ",") <~ "]"  ^^ {
  case el => Liste(el)
}

your original parse means to have a list like [True,FalseTrue], is that what you want?