strongInsert :: Eq a => TECtxtJudgment a -> TEContext a -> TEContext a
strongInsert (v,t) ctxt = if length (filter (\(x,_) -> x == v) ctxt) > 0
                          then error "strongInsert failed"
                          else (v,t) : ctxt
strongInsert :: Eq a => TECtxtJudgment a -> TEContext a -> TEContext a
strongInsert (v,t) ctxt = if length (filter (\(x,_) -> x == v) ctxt) > 0
                          then error "strongInsert failed"
                          else (v,t) : ctxt
strongInsert (v,t) ctxt = if length (filter (\(x,_) -> x == v) ctxt) > 0
                          then error "strongInsert failed"
                          else (v,t) : ctxt