(Program
  (If
    (Not
      (Send
      { (Identifier)
      ->(Identifier) }))
    (Statements
    {+(Send
      {+(Identifier)+})+})
  { (Empty)
  ->(Send
    {+(Identifier)+}) })
{-(If
  {-(Not
    {-(Send
      {-(Identifier)-})-})-}
  {-(Statements)-}
  {-(Empty)-})-})