3 import Language.Haskell.Syntax
5 main = do show_add exp_adder; show_add rec_adder;
7 show_add f = do print ("Sum: " ++ (displaysigs s)); print ("Carry: " ++ (displaysig c))
9 a = [High, High, High, High]
10 b = [Low, Low, Low, High]
13 -- Combinatoric stateless no-carry adder
15 no_carry_adder :: (Bit, Bit) -> Bit
16 no_carry_adder (a, b) = a `hwxor` b
18 -- Combinatoric stateless half adder
20 half_adder :: (Bit, Bit) -> (Bit, Bit)
22 ( a `hwxor` b, a `hwand` b )
24 -- Combinatoric stateless full adder
25 -- (A, B, C) -> (S, C)
26 full_adder :: (Bit, Bit, Bit) -> (Bit, Bit)
27 full_adder (a, b, cin) = (s, c)
29 s = a `hwxor` b `hwxor` cin
30 c = a `hwand` b `hwor` (cin `hwand` (a `hwxor` b))
34 -- [a] -> [b] -> ([s], cout)
35 exp_adder :: ([Bit], [Bit]) -> ([Bit], Bit)
37 exp_adder ([a3,a2,a1,a0], [b3,b2,b1,b0]) =
38 ([s3, s2, s1, s0], c3)
40 (s0, c0) = full_adder (a0, b0, Low)
41 (s1, c1) = full_adder (a1, b1, c0)
42 (s2, c2) = full_adder (a2, b2, c1)
43 (s3, c3) = full_adder (a3, b3, c2)
45 -- Any number of bits adder
47 -- [a] -> [b] -> ([s], cout)
48 rec_adder :: ([Bit], [Bit]) -> ([Bit], Bit)
50 rec_adder ([], []) = ([], Low)
51 rec_adder ((a:as), (b:bs)) =
54 (rest, cin) = rec_adder (as, bs)
55 (s, cout) = full_adder (a, b, cin)
57 -- Four bit adder, using the continous adder below
58 -- [a] -> [b] -> ([s], cout)
60 -- ([s3, s2, s1, s0], c)
62 -- ((s0, _):(s1, _):(s2, _):(s3, c):_) = con_adder (zip ((reverse as) ++ lows) ((reverse bs) ++ lows))
64 -- Continuous sequential version
65 -- Stream a -> Stream b -> Stream (sum, cout)
66 --con_adder :: Stream (Bit, Bit) -> Stream (Bit, Bit)
68 -- Forward to con_adder_int, but supply an initial state
70 -- con_adder_int pin Low
72 -- Stream a -> Stream b -> state -> Stream (s, c)
73 --con_adder_int :: Stream (Bit, Bit) -> Bit -> Stream (Bit, Bit)
74 --con_adder_int ((a,b):rest) cin =
75 -- (s, cout) : con_adder_int rest cout
77 -- (s, cout) = full_adder a b cin
79 -- vim: set ts=8 sw=2 sts=2 expandtab: