refactor(users/glittershark): Rename to grfn r/2485

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>

1 files changed, 252 insertions, 0 deletions

diff --git a/users/grfn/xanthous/src/Xanthous/Util.hs b/users/grfn/xanthous/src/Xanthous/Util.hs
new file mode 100644
index 0000000000..524ad4819d
--- /dev/null
+++ b/users/grfn/xanthous/src/Xanthous/Util.hs
@@ -0,0 +1,252 @@
+{-# LANGUAGE BangPatterns          #-}
+{-# LANGUAGE AllowAmbiguousTypes   #-}
+{-# LANGUAGE QuantifiedConstraints #-}
+--------------------------------------------------------------------------------
+module Xanthous.Util
+  ( EqEqProp(..)
+  , EqProp(..)
+  , foldlMapM
+  , foldlMapM'
+  , between
+
+  , appendVia
+
+    -- * Foldable
+    -- ** Uniqueness
+    -- *** Predicates on uniqueness
+  , isUniqueOf
+  , isUnique
+    -- *** Removing all duplicate elements in n * log n time
+  , uniqueOf
+  , unique
+    -- *** Removing sequentially duplicate elements in linear time
+  , uniqOf
+  , uniq
+    -- ** Bag sequence algorithms
+  , takeWhileInclusive
+  , smallestNotIn
+  , removeVectorIndex
+  , maximum1
+  , minimum1
+
+    -- * Combinators
+  , times, times_
+
+    -- * Type-level programming utils
+  , KnownBool(..)
+  ) where
+--------------------------------------------------------------------------------
+import           Xanthous.Prelude hiding (foldr)
+--------------------------------------------------------------------------------
+import           Test.QuickCheck.Checkers
+import           Data.Foldable (foldr)
+import           Data.Monoid
+import           Data.Proxy
+import qualified Data.Vector as V
+import           Data.Semigroup (Max(..), Min(..))
+import           Data.Semigroup.Foldable
+--------------------------------------------------------------------------------
+
+newtype EqEqProp a = EqEqProp a
+  deriving newtype Eq
+
+instance Eq a => EqProp (EqEqProp a) where
+  (=-=) = eq
+
+foldlMapM :: forall g b a m. (Foldable g, Monoid b, Applicative m) => (a -> m b) -> g a -> m b
+foldlMapM f = foldr f' (pure mempty)
+  where
+    f' :: a -> m b -> m b
+    f' x = liftA2 mappend (f x)
+
+-- Strict in the monoidal accumulator. For monads strict
+-- in the left argument of bind, this will run in constant
+-- space.
+foldlMapM' :: forall g b a m. (Foldable g, Monoid b, Monad m) => (a -> m b) -> g a -> m b
+foldlMapM' f xs = foldr f' pure xs mempty
+  where
+  f' :: a -> (b -> m b) -> b -> m b
+  f' x k bl = do
+    br <- f x
+    let !b = mappend bl br
+    k b
+
+between
+  :: Ord a
+  => a -- ^ lower bound
+  -> a -- ^ upper bound
+  -> a -- ^ scrutinee
+  -> Bool
+between lower upper x = x >= lower && x <= upper
+
+-- |
+-- >>> appendVia Sum 1 2
+-- 3
+appendVia :: (Rewrapping s t, Semigroup s) => (Unwrapped s -> s) -> Unwrapped s -> Unwrapped s -> Unwrapped s
+appendVia wrap x y = op wrap $ wrap x <> wrap y
+
+--------------------------------------------------------------------------------
+
+-- | Returns True if the targets of the given 'Fold' are unique per the 'Ord' instance for @a@
+--
+-- >>> isUniqueOf (folded . _1) ([(1, 2), (2, 2), (3, 2)] :: [(Int, Int)])
+-- True
+--
+-- >>> isUniqueOf (folded . _2) ([(1, 2), (2, 2), (3, 2)] :: [(Int, Int)])
+-- False
+--
+-- @
+-- 'isUniqueOf' :: Ord a => 'Getter' s a     -> s -> 'Bool'
+-- 'isUniqueOf' :: Ord a => 'Fold' s a       -> s -> 'Bool'
+-- 'isUniqueOf' :: Ord a => 'Lens'' s a      -> s -> 'Bool'
+-- 'isUniqueOf' :: Ord a => 'Iso'' s a       -> s -> 'Bool'
+-- 'isUniqueOf' :: Ord a => 'Traversal'' s a -> s -> 'Bool'
+-- 'isUniqueOf' :: Ord a => 'Prism'' s a     -> s -> 'Bool'
+-- @
+isUniqueOf :: Ord a => Getting (Endo (Set a, Bool)) s a -> s -> Bool
+isUniqueOf aFold = orOf _2 . foldrOf aFold rejectUnique (mempty, True)
+ where
+  rejectUnique x (seen, acc)
+    | seen ^. contains x = (seen, False)
+    | otherwise          = (seen & contains x .~ True, acc)
+
+-- | Returns true if the given 'Foldable' container contains only unique
+-- elements, as determined by the 'Ord' instance for @a@
+--
+-- >>> isUnique ([3, 1, 2] :: [Int])
+-- True
+--
+-- >>> isUnique ([1, 1, 2, 2, 3, 1] :: [Int])
+-- False
+isUnique :: (Foldable f, Ord a) => f a -> Bool
+isUnique = isUniqueOf folded
+
+
+-- | O(n * log n). Returns a monoidal, 'Cons'able container (a list, a Set,
+-- etc.) consisting of the unique (per the 'Ord' instance for @a@) targets of
+-- the given 'Fold'
+--
+-- >>> uniqueOf (folded . _2) ([(1, 2), (2, 2), (3, 2), (4, 3)] :: [(Int, Int)]) :: [Int]
+-- [2,3]
+--
+-- @
+-- 'uniqueOf' :: Ord a => 'Getter' s a     -> s -> [a]
+-- 'uniqueOf' :: Ord a => 'Fold' s a       -> s -> [a]
+-- 'uniqueOf' :: Ord a => 'Lens'' s a      -> s -> [a]
+-- 'uniqueOf' :: Ord a => 'Iso'' s a       -> s -> [a]
+-- 'uniqueOf' :: Ord a => 'Traversal'' s a -> s -> [a]
+-- 'uniqueOf' :: Ord a => 'Prism'' s a     -> s -> [a]
+-- @
+uniqueOf
+  :: (Monoid c, Ord w, Cons c c w w) => Getting (Endo (Set w, c)) a w -> a -> c
+uniqueOf aFold = snd . foldrOf aFold rejectUnique (mempty, mempty)
+ where
+  rejectUnique x (seen, acc)
+    | seen ^. contains x = (seen, acc)
+    | otherwise          = (seen & contains x .~ True, cons x acc)
+
+-- | Returns a monoidal, 'Cons'able container (a list, a Set, etc.) consisting
+-- of the unique (per the 'Ord' instance for @a@) contents of the given
+-- 'Foldable' container
+--
+-- >>> unique [1, 1, 2, 2, 3, 1] :: [Int]
+-- [2,3,1]
+
+-- >>> unique [1, 1, 2, 2, 3, 1] :: Set Int
+-- fromList [3,2,1]
+unique :: (Foldable f, Cons c c a a, Ord a, Monoid c) => f a -> c
+unique = uniqueOf folded
+
+--------------------------------------------------------------------------------
+
+-- | O(n). Returns a monoidal, 'Cons'able container (a list, a Vector, etc.)
+-- consisting of the targets of the given 'Fold' with sequential duplicate
+-- elements removed
+--
+-- This function (sorry for the confusing name) differs from 'uniqueOf' in that
+-- it only compares /sequentially/ duplicate elements (and thus operates in
+-- linear time).
+-- cf 'Data.Vector.uniq' and POSIX @uniq@ for the name
+--
+-- >>> uniqOf (folded . _2) ([(1, 2), (2, 2), (3, 1), (4, 2)] :: [(Int, Int)]) :: [Int]
+-- [2,1,2]
+--
+-- @
+-- 'uniqOf' :: Eq a => 'Getter' s a     -> s -> [a]
+-- 'uniqOf' :: Eq a => 'Fold' s a       -> s -> [a]
+-- 'uniqOf' :: Eq a => 'Lens'' s a      -> s -> [a]
+-- 'uniqOf' :: Eq a => 'Iso'' s a       -> s -> [a]
+-- 'uniqOf' :: Eq a => 'Traversal'' s a -> s -> [a]
+-- 'uniqOf' :: Eq a => 'Prism'' s a     -> s -> [a]
+-- @
+uniqOf :: (Monoid c, Cons c c w w, Eq w) => Getting (Endo (Maybe w, c)) a w -> a -> c
+uniqOf aFold = snd . foldrOf aFold rejectSeen (Nothing, mempty)
+  where
+    rejectSeen x (Nothing, acc) = (Just x, x <| acc)
+    rejectSeen x tup@(Just a, acc)
+      | x == a     = tup
+      | otherwise = (Just x, x <| acc)
+
+-- | O(n). Returns a monoidal, 'Cons'able container (a list, a Vector, etc.)
+-- consisting of the targets of the given 'Foldable' container with sequential
+-- duplicate elements removed
+--
+-- This function (sorry for the confusing name) differs from 'unique' in that
+-- it only compares /sequentially/ unique elements (and thus operates in linear
+-- time).
+-- cf 'Data.Vector.uniq' and POSIX @uniq@ for the name
+--
+-- >>> uniq [1, 1, 1, 2, 2, 2, 3, 3, 1] :: [Int]
+-- [1,2,3,1]
+--
+-- >>> uniq [1, 1, 1, 2, 2, 2, 3, 3, 1] :: Vector Int
+-- [1,2,3,1]
+--
+uniq :: (Foldable f, Eq a, Cons c c a a, Monoid c) => f a -> c
+uniq = uniqOf folded
+
+-- | Like 'takeWhile', but inclusive
+takeWhileInclusive :: (a -> Bool) -> [a] -> [a]
+takeWhileInclusive _ [] = []
+takeWhileInclusive p (x:xs) = x : if p x then takeWhileInclusive p xs else []
+
+-- | Returns the smallest value not in a list
+smallestNotIn :: (Ord a, Bounded a, Enum a) => [a] -> a
+smallestNotIn xs = case uniq $ sort xs of
+  [] -> minBound
+  xs'@(x : _)
+    | x > minBound -> minBound
+    | otherwise
+    -> snd . headEx . filter (uncurry (/=)) $ zip (xs' ++ [minBound]) [minBound..]
+
+-- | Remove the element at the given index, if any, from the given vector
+removeVectorIndex :: Int -> Vector a -> Vector a
+removeVectorIndex idx vect =
+  let (before, after) = V.splitAt idx vect
+  in before <> fromMaybe Empty (tailMay after)
+
+maximum1 :: (Ord a, Foldable1 f) => f a -> a
+maximum1 = getMax . foldMap1 Max
+
+minimum1 :: (Ord a, Foldable1 f) => f a -> a
+minimum1 = getMin . foldMap1 Min
+
+times :: (Applicative f, Num n, Enum n) => n -> (n -> f b) -> f [b]
+times n f = traverse f [1..n]
+
+times_ :: (Applicative f, Num n, Enum n) => n -> f a -> f [a]
+times_ n fa = times n (const fa)
+
+--------------------------------------------------------------------------------
+
+-- | This class gives a boolean associated with a type-level bool, a'la
+-- 'KnownSymbol', 'KnownNat' etc.
+class KnownBool (bool :: Bool) where
+  boolVal' :: forall proxy. proxy bool -> Bool
+  boolVal' _ = boolVal @bool
+
+  boolVal :: Bool
+  boolVal = boolVal' $ Proxy @bool
+
+instance KnownBool 'True where boolVal = True
+instance KnownBool 'False where boolVal = False