unfoldable 0.1.0 → 0.2.0

raw patch · 3 files changed

+15/−8 lines, 3 files

Files

• src/Data/Splittable.hs +9/−7
• src/Data/Unfoldable.hs +5/−0
• unfoldable.cabal +1/−1

@@ -33,17 +33,20 @@     n `mod'` m = n `mod` m   data Left = L+-- | Always choose the first item. instance Splittable Left where   split = replicate   choose fs = head fs   getInt L = 0  data Right = R+-- | Always choose the last item. instance Splittable Right where   split = replicate   choose fs = last fs   getInt R = 0 +-- | Choose randomly instance Splittable R.StdGen where   split 0 _ = []   split 1 s = [s]@@ -51,6 +54,8 @@   choose fs s = let (n, s') = R.next s in fs !! (n `mod` length fs) $ s'   getInt = fst . R.next +-- | The 'Integer' instance uses modulo to choose, and splits breadth-first by +-- distributing bits in a round-robin fashion. instance Splittable Integer where   split n t = split' 1 (t, replicate n 0)     where@@ -59,23 +64,20 @@   choose fs s = let (s', n) = s `divMod` toInteger (length fs) in fs !! fromInteger n $ s'   getInt = fromInteger +-- | The @(a, b)@ instance uses only @a@ for 'choose' and @b@ for 'getInt'. instance (Splittable a, Splittable b) => Splittable (a, b) where   split n (a, b) = zip (split n a) (split n b)   choose = uncurry . choose . map curry-  getInt (a, b) = go (getInt a) (getInt b)-    where-      go 0 0 = 0-      go m n = go m' n' * 4 + mb * 2 + nb-        where-          (m', mb) = m `divMod` 2-          (n', nb) = n `divMod` 2+  getInt (_, b) = getInt b +-- | Choose between 2 ways to split and choose. instance (Splittable a, Splittable b) => Splittable (Either a b) where   split n   = either (map Left . split n) (map Right . split n)   choose fs = either (choose (map (. Left) fs)) (choose (map (. Right) fs))   getInt (Left a) = getInt a * 2   getInt (Right a) = getInt a * 2 + 1 +-- | Reverse the split output and the choose input. instance Splittable s => Splittable (Dual s) where   split n = map Dual . reverse . split n . getDual   choose fs = choose (map (. Dual) $ reverse fs) . getDual

@@ -53,18 +53,23 @@   -- and an initial seed, generate a structure.   unfoldMap :: Splittable s => (s -> a) -> s -> f a +-- | The same as @unfoldMap id@. unfold :: (Unfoldable f, Splittable s) => s -> f s unfold = unfoldMap id +-- | Always choose the first constructor. leftMost :: Unfoldable f => f () leftMost = unfoldMap (const ()) L +-- | Always choose the last constructor. rightMost :: Unfoldable f => f () rightMost = unfoldMap (const ()) R +-- | Count the number of times 'to' is used, and split the seed in that many parts. spread :: Splittable s => State ([s], Int) a -> s -> a spread f s = let (a, (_, i)) = runState f (split i s, 0) in a +-- | Signal to 'spread' that this is a subpart that needs a seed. to :: (s -> a) -> State ([s], Int) a to f = state $ \(ss, i) -> (f (head ss), (tail ss, i + 1)) 

@@ -1,5 +1,5 @@ Name:                unfoldable-Version:             0.1.0+Version:             0.2.0 Synopsis:            Class of data structures that can be unfolded from a seed value. Homepage:            https://github.com/sjoerdvisscher/unfoldable License:             BSD3