replTail (\t' -> h (setSp spOff spOff' (ZTail (middle spOff m) t'))) spOff' t
where spOff' = slot' (Just bid) + widthInBytes (typeWidth gcWord)
replTail h spOff (ZTail m t) = replTail (h . ZTail (middle spOff m)) spOff t
replTail (\t' -> h (setSp spOff spOff' (ZTail (middle spOff m) t'))) spOff' t
where spOff' = slot' (Just bid) + widthInBytes (typeWidth gcWord)
replTail h spOff (ZTail m t) = replTail (h . ZTail (middle spOff m)) spOff t