urbit/pkg/hs/proto/lib/SimpleNoun.hs
2020-01-22 18:58:22 -08:00

123 lines
2.4 KiB
Haskell

module SimpleNoun where
import ClassyPrelude
import Numeric.Natural
import qualified Ur.Noun as N
type Atom = Natural
type Noun = Tree Atom
data Tree a
= A !a
| C !(Tree a) !(Tree a)
deriving (Eq, Ord, Read, Functor, Generic)
instance Hashable a => Hashable (Tree a)
data Fern a
= FernA !a
| FernF [Fern a]
toFern :: Tree a -> Fern a
toFern = \case
A a -> FernA a
C h t -> case toFern t of
a@FernA{} -> FernF [toFern h, a]
FernF fs -> FernF (toFern h : fs)
instance Show a => Show (Fern a) where
show = \case
FernA a -> show a
FernF xs -> "[" <> intercalate " " (map show xs) <> "]"
instance Show a => Show (Tree a) where
show = show . toFern
yes, no :: Noun
yes = A 0
no = A 1
loob :: Bool -> Noun
loob = \case
True -> yes
False -> no
textToAtom :: Text -> Atom
textToAtom t = case N.textToUtf8Atom t of
N.A a -> a
showA :: Atom -> String
showA a = show (N.A a)
tshowA :: Atom -> Text
tshowA = pack . showA
-- | Tree address
type Axis = Atom
data Dir = L | R
deriving (Eq, Ord, Enum, Read, Show)
type Path = [Dir]
-- some stuff from hoon.hoon
cap :: Axis -> Dir
cap = \case
2 -> L
3 -> R
a | a <= 1 -> error "cap: bad axis"
| otherwise -> cap (div a 2)
mas :: Axis -> Axis
mas = \case
2 -> 1
3 -> 1
a | a <= 1 -> error "mas: bad axis"
| otherwise -> (mod a 2) + 2 * mas (div a 2)
capMas :: Axis -> (Dir, Axis)
capMas = \case
2 -> (L, 1)
3 -> (R, 1)
a | a <= 1 -> error "capMas: bad axis"
| otherwise -> (d, (mod a 2) + 2 * r)
where
(d, r) = capMas (div a 2)
peg :: Axis -> Axis -> Axis
peg a = \case
1 -> a
2 -> a * 2
3 -> a * 2 + 1
b -> (mod b 2) + 2 * peg a (div b 2)
axis :: Axis -> Tree a -> Tree a
axis 1 n = n
axis (capMas -> (d, r)) (C n m) = case d of
L -> axis r n
R -> axis r m
axis a _ = error ("bad axis: " ++ show a)
edit :: Axis -> Tree a -> Tree a -> Tree a
edit 1 v n = v
edit (capMas -> (d, r)) v (C n m) = case d of
L -> C (edit r v n) m
R -> C n (edit r v m)
edit a _ _ = error ("bad edit: " ++ show a)
-- Write an axis as a binary number; e.g. 5 as 101.
-- The rule is: after droping the 1 in the msb, you read from left to right.
-- 0 becomes L and 1 becomes R. So 5 becomes [L,R]
toPath :: Axis -> Path
toPath = \case
1 -> []
(capMas -> (d, r)) -> d : toPath r
toAxis :: Path -> Axis
toAxis = foldl' step 1
where
step r = \case
L -> 2 * r
R -> 2 * r + 1