---
bin_op := rules "expr" "subtract" "expr"
  bin_op := rules "expr" "divide" "expr"
    bin_op := rules "expr" "multiply" "expr"
      bin_op := rules "expr" "add" "expr"
        int := lexemes "INT"
          INT "1" (1, 1)
        add := lexemes "+"
          + "+" (1, 3)
        int := lexemes "INT"
          INT "2" (1, 5)
      multiply := lexemes "*"
        * "*" (1, 7)
      int := lexemes "INT"
        INT "3" (1, 9)
    divide := lexemes "/"
      / "/" (1, 11)
    int := lexemes "INT"
      INT "4" (1, 13)
  subtract := lexemes "-"
    - "-" (1, 15)
  int := lexemes "INT"
    INT "5" (1, 17)