Capturing repeated expressions

[Matthew Sainsbury]

I've got a simple grammar like so:

grammar Test
  rule array
    '[' letter (',' letter)* ']'
    {
      def eval
        #???
      end
    }
  end

  rule letter
    [a-zA-Z] 1..1
    {
      def eval
        text_value
      end
    }
  end
end

A sample string in the grammar is "[a,b,c,d]"

I would like the eval method on the array rule to return an array of strings ["a", "b", "c", "d"], but I'm not sure how to do that. I can get the first element by doing:

def eval
  [letter.eval]
end

which would return ["a"]. How do I capture the following letter instances in the expression?

[Clifford Heath]

Add a label to your iterated group and append the items to a list containing the head item:

rule array

  '[' letter tail:(',' letter) ']'

  {

    def eval

      [letter.text_value] + tail.map{|e| e.letter.text_value}

    end

  }

You can also do this with inject if you prefer that style.

Clifford Heath

[Clifford Heath]

Gah, forgot the * on the iterated group. You get the picture though.

[Clifford Heath]

Also, it's tail.elements.map{...}

Sorry for the noise, folk.