module Logic.Predicate.Illegal where

-- some illegal states are representable
-- e.g. a function with arity 2 having 3 arguments

data Formula
  = Not Formula
  | Or Formula Formula
  | And Formula Formula
  | Implies Formula Formula
  | Iff Formula Formula
  | Forall String Formula
  | Exists String Formula
  | Predicate String [Term]
  deriving Show

data Term
  = Variable String
  | Function String [Term]
  deriving Show