Scala parser left recursion with List

Question

My problem is that I would like to implement a grammar that (on paper) looks like this:

functionCall = expression "(" [{expression ";"} expression ] ")"

Here are some examples:

• foo(var)
• foo(var1; var2)
• foo()
• foo(var1; var2; var3)

With this specified grammar this should also work:

foo(var1)()

foo(var1) => expression

"("

")"

With this grammar a left recursion occurs and I do not know how to handle it.

I am using the Scala parser library to realize this grammar.

I have looked into some post especially this one Recursive definitions with scala-parser-combinators to figure out a solution.

I have found many solutions for problems that look similar to this:

expression ~ "." ~ expression

I tried to replicate the Solution for my problem, but I was not able to achieve success.

My simplified code looks like this:

sealed trait Baz
case class Start(code: Baz) extends Baz
case class FunctionCall(call: Baz, arg: List[Baz]) extends Baz
case class foo(text: String) extends Baz
case class bar(nr: Int) extends Baz

class ExpParser extends JavaTokenParsers {

  def start: Parser[Start] = expression ^^ {s => Start(s)}

  def expression: Parser[Baz] = foo | bar | functionCall 

  private val foo: Parser[Foo] = "[a-z]*".r ^^ {f => Foo(f)}
  private val bar: Parser[Bar] = "[0-9]*".r ^^ {b => Bar(b)}

  private val functionCall: Parser[Baz] = expression ~ "(" ~  repsep(expression, ";") <~ ")" ^^ {case l~_~r => FunctionCall(l,r)}
}

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

I have tried to use chainl1 but reading the Implementation it seems at least to me that this won't work for my problem.

I would like to know if there is any way to change my code so that I can avoid this left recursion and keep the data structure of functionCall with the List.

If I was unclear about anything I apologize and would be glad to answer you.

Any help is very appreciated!