basic_lisp.rb

grammar BasicLISP
  rule expression
    "(" (expression / method_call) ")"
  end

  rule method_call
    [\w]+ argument*
  end

  rule argument
    [\s]+ (expression / number / string)
  end

  rule number
    [\d]+
  end

  rule string
    '"' [\w]+ '"'
  end
end