varTypeJudgment :: Eq a
                => a                        -- Type of variables
                -> TEContext a              -- Typing context, parameterized
                                            -- by the type of term variables
                -> Maybe (TECtxtJudgment a) -- Judgement that involves
                                            -- that variable, if any
varTypeJudgment x = filterElement ((x ==) . fst)
varTypeJudgment :: Eq a
                => a                        -- Type of variables
                -> TEContext a              -- Typing context, parameterized
                                            -- by the type of term variables
                -> Maybe (TECtxtJudgment a)
varTypeJudgment x = filterElement ((x ==) . fst)
varTypeJudgment x = filterElement ((x ==) . fst)