Judgement = Term

Term = Var
     | "fun" Var "->" Term
     | Term Term
     | "shift" Var "->" Term
     | "<" Term ">"
     | "(" Term ")"

Type = Var
     | Type "/" Type "->" Type "/" Type
     | "(" Type ")"

Var = variable starting with a lower case letter
    | metavariable starting with an upper case letter

Env = Var
    | Var ":" Type "," Env
    | "(" Env ")"