\begin{code}
-- THESE ARE DIRECTION SENSITIVE!
+spARelToInt :: Int{-VirtualSpAOffset-} -> Int{-VirtualSpAOffset-} -> Int
+spBRelToInt :: Int{-VirtualSpBOffset-} -> Int{-VirtualSpBOffset-} -> Int
+
spARelToInt spA off = spA - off -- equiv to: AREL(spA - off)
spBRelToInt spB off = off - spB -- equiv to: BREL(spB - off)
\end{code}