buildXfm m f (x:xs)   = buildXfm m (g . f) xs
    where g = fromJust (M.lookup x m)
buildXfm m f (x:xs)   = buildXfm m (g . f) xs
    where g = fromJust (M.lookup x m)
buildXfm m f (x:xs)   = buildXfm m (g . f) xs
    where g = fromJust (M.lookup x m)