dup :: Bit -> (Bit, Bit)
dup a = (a, a)
+-- Not really an adder either, but a simple stateful example (D-flipflop)
+dff :: Bit -> Bit -> (Bit, Bit)
+dff d s = (s', q)
+ where
+ q = s
+ s' = d
+
-- Combinatoric stateless no-carry adder
-- A -> B -> S
no_carry_adder :: (Bit, Bit) -> Bit