-- This function is from Sim.hs, but we redefine it here so it can get inlined
-- by default.
+stateless :: (i -> o) -> (i -> () -> ((), o))
stateless f = \i s -> (s, f i)
show_add f = do print ("Sum: " ++ (displaysigs s)); print ("Carry: " ++ (displaysig c))
b = [Low, Low, Low, High]
(s, c) = f (a, b)
+mux2 :: Bit -> (Bit, Bit) -> Bit
+mux2 Low (a, b) = a
+mux2 High (a, b) = b
+
-- Not really an adder, but this is nice minimal hardware description
wire :: Bit -> Bit
wire a = a
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
+
+type ShifterState = (Bit, Bit, Bit, Bit)
+shifter :: Bit -> ShifterState -> (ShifterState, Bit)
+shifter a s =
+ (s', o)
+ where
+ s' = (a, b, c, d)
+ (b, c, d, o) = s
+
-- Combinatoric stateless no-carry adder
-- A -> B -> S
no_carry_adder :: (Bit, Bit) -> Bit
-- Combinatoric stateless half adder
-- A -> B -> (S, C)
half_adder :: (Bit, Bit) -> (Bit, Bit)
+{-# NOINLINE half_adder #-}
half_adder (a, b) =
( a `hwxor` b, a `hwand` b )