(VAR b e r)
(RULES
  pow(b, e) -> condLoop(e > 0, b, e, 1)

  condLoop(FALSE, b, e, r) -> r
  condLoop(TRUE, b, e, r)  -> condMod(e %@z 2 = 1, b, e, r)

  condMod(FALSE, b, e, r) -> sqBase(b, e, r)
  condMod(TRUE, b, e, r)  -> sqBase(b, e, r*b)

  sqBase(b, e, r) -> halfExp(b*b, e, r)

  halfExp(b, e, r) -> condLoop(e > 0, b, e/2, r)
)