-module Adders (main, no_carry_adder) where
+module Adders where
import Bits
import Language.Haskell.Syntax
b = [Low, Low, Low, High]
(s, c) = f (a, b)
--- Combinatoric no-carry adder
+-- Not really an adder, but this is nice minimal hardware description
+wire :: Bit -> Bit
+wire a = a
+
+-- Not really an adder either, but a slightly more complex example
+inv :: Bit -> Bit
+inv a = hwnot a
+
+-- Not really an adder either, but a slightly more complex example
+invinv :: Bit -> Bit
+invinv a = hwnot (hwnot a)
+
+-- Not really an adder either, but a slightly more complex example
+dup :: Bit -> (Bit, Bit)
+dup a = (a, a)
+
+-- Combinatoric stateless no-carry adder
-- A -> B -> S
no_carry_adder :: (Bit, Bit) -> Bit
no_carry_adder (a, b) = a `hwxor` b
--- Combinatoric (one-bit) full adder
+-- Combinatoric stateless half adder
+-- A -> B -> (S, C)
+half_adder :: (Bit, Bit) -> (Bit, Bit)
+half_adder (a, b) =
+ ( a `hwxor` b, a `hwand` b )
+
+-- Combinatoric stateless full adder
-- (A, B, C) -> (S, C)
full_adder :: (Bit, Bit, Bit) -> (Bit, Bit)
full_adder (a, b, cin) = (s, c)
where
- s = a `hwxor` b `hwxor` cin
- c = a `hwand` b `hwor` (cin `hwand` (a `hwxor` b))
+ x = a `hwxor` b
+ s = x `hwxor` cin
+ c = a `hwand` b `hwor` (cin `hwand` x)
-- Four bit adder
-- Explicit version