tLookup ((t,a):xs) t' | t /= t'   = Just a
                      | otherwise = tLookup xs t'
tLookup ((t,a):xs) t' | t /= t'   = Just a
                      | otherwise = tLookup xs t'
tLookup ((t,a):xs) t' | t /= t'   = Just a
                      | otherwise = tLookup xs t'