From 6266c5d32f9ff651fcfc3a4cc0c68e89da56ca65 Mon Sep 17 00:00:00 2001
From: Griffin Smith <grfn@gws.fyi>
Date: Sun, 11 Apr 2021 17:53:27 -0400
Subject: refactor(users/glittershark): Rename to grfn

Rename my //users directory and all places that refer to glittershark to
grfn, including nix references and documentation.

This may require some extra attention inside of gerrit's database after
it lands to allow me to actually push things.

Change-Id: I4728b7ec2c60024392c1c1fa6e0d4a59b3e266fa
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2933
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>
Reviewed-by: lukegb <lukegb@tvl.fyi>
Reviewed-by: glittershark <grfn@gws.fyi>
---
 users/grfn/xanthous/src/Xanthous/Random.hs | 118 +++++++++++++++++++++++++++++
 1 file changed, 118 insertions(+)
 create mode 100644 users/grfn/xanthous/src/Xanthous/Random.hs

(limited to 'users/grfn/xanthous/src/Xanthous/Random.hs')

diff --git a/users/grfn/xanthous/src/Xanthous/Random.hs b/users/grfn/xanthous/src/Xanthous/Random.hs
new file mode 100644
index 000000000000..6d34109df7f8
--- /dev/null
+++ b/users/grfn/xanthous/src/Xanthous/Random.hs
@@ -0,0 +1,118 @@
+--------------------------------------------------------------------------------
+{-# LANGUAGE UndecidableInstances #-}
+{-# OPTIONS_GHC -fno-warn-orphans #-}
+--------------------------------------------------------------------------------
+module Xanthous.Random
+  ( Choose(..)
+  , ChooseElement(..)
+  , Weighted(..)
+  , evenlyWeighted
+  , weightedBy
+  , subRand
+  , chance
+  , chooseSubset
+  ) where
+--------------------------------------------------------------------------------
+import Xanthous.Prelude
+--------------------------------------------------------------------------------
+import           Data.List.NonEmpty (NonEmpty(..))
+import           Control.Monad.Random.Class (MonadRandom(getRandomR, getRandom))
+import           Control.Monad.Random (Rand, evalRand, mkStdGen, StdGen)
+import           Data.Functor.Compose
+import           Data.Random.Shuffle.Weighted
+import           Data.Random.Distribution
+import           Data.Random.Distribution.Uniform
+import           Data.Random.Distribution.Uniform.Exclusive
+import           Data.Random.Sample
+import qualified Data.Random.Source as DRS
+--------------------------------------------------------------------------------
+
+instance {-# INCOHERENT #-} (Monad m, MonadRandom m) => DRS.MonadRandom m where
+  getRandomWord8 = getRandom
+  getRandomWord16 = getRandom
+  getRandomWord32 = getRandom
+  getRandomWord64 = getRandom
+  getRandomDouble = getRandom
+  getRandomNByteInteger n = getRandomR (0, 256 ^ n)
+
+class Choose a where
+  type RandomResult a
+  choose :: MonadRandom m => a -> m (RandomResult a)
+
+newtype ChooseElement a = ChooseElement a
+
+instance MonoFoldable a => Choose (ChooseElement a) where
+  type RandomResult (ChooseElement a) = Maybe (Element a)
+  choose (ChooseElement xs) = do
+    chosenIdx <- getRandomR (0, olength xs - 1)
+    let pick _ (Just x) = Just x
+        pick (x, i) Nothing
+          | i == chosenIdx = Just x
+          | otherwise = Nothing
+    pure $ ofoldr pick Nothing $ zip (toList xs) [0..]
+
+instance MonoFoldable a => Choose (NonNull a) where
+  type RandomResult (NonNull a) = Element a
+  choose
+    = fmap (fromMaybe (error "unreachable")) -- why not lol
+    . choose
+    . ChooseElement
+    . toNullable
+
+instance Choose (NonEmpty a) where
+  type RandomResult (NonEmpty a) = a
+  choose = choose . fromNonEmpty @[_]
+
+instance Choose (a, a) where
+  type RandomResult (a, a) = a
+  choose (x, y) = choose (x :| [y])
+
+newtype Weighted w t a = Weighted (t (w, a))
+  deriving (Functor, Foldable) via (t `Compose` (,) w)
+
+instance Traversable t => Traversable (Weighted w t) where
+  traverse f (Weighted twa) = Weighted <$> (traverse . traverse) f twa
+
+evenlyWeighted :: [a] -> Weighted Int [] a
+evenlyWeighted = Weighted . itoList
+
+-- | Weight the elements of some functor by a function. Larger values of 'w' per
+-- its 'Ord' instance will be more likely to be generated
+weightedBy :: Functor t => (a -> w) -> t a -> Weighted w t a
+weightedBy weighting xs = Weighted $ (weighting &&& id) <$> xs
+
+instance (Num w, Ord w, Distribution Uniform w, Excludable w) => Choose (Weighted w [] a) where
+  type RandomResult (Weighted w [] a) = Maybe a
+  choose (Weighted ws) = sample $ headMay <$> weightedSample 1 ws
+
+instance (Num w, Ord w, Distribution Uniform w, Excludable w) => Choose (Weighted w NonEmpty a) where
+  type RandomResult (Weighted w NonEmpty a) = a
+  choose (Weighted ws) =
+    sample
+    $ fromMaybe (error "unreachable") . headMay
+    <$> weightedSample 1 (toList ws)
+
+subRand :: MonadRandom m => Rand StdGen a -> m a
+subRand sub = evalRand sub . mkStdGen <$> getRandom
+
+-- | Has a @n@ chance of returning 'True'
+--
+-- eg, chance 0.5 will return 'True' half the time
+chance
+  :: (Num w, Ord w, Distribution Uniform w, Excludable w, MonadRandom m)
+  => w
+  -> m Bool
+chance n = choose $ weightedBy (bool 1 (n * 2)) bools
+
+-- | Choose a random subset of *about* @w@ of the elements of the given
+-- 'Witherable' structure
+chooseSubset :: ( Num w, Ord w, Distribution Uniform w, Excludable w
+               , Witherable t
+               , MonadRandom m
+               ) => w -> t a -> m (t a)
+chooseSubset = filterA . const . chance
+
+--------------------------------------------------------------------------------
+
+bools :: NonEmpty Bool
+bools = True :| [False]
-- 
cgit 1.4.1