231 lines
6.7 KiB
Idris
231 lines
6.7 KiB
Idris
module Quox.Context
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import Quox.Syntax.Shift
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import Quox.Pretty
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import Data.DPair
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import Data.Nat
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import Data.SnocList
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import Data.Vect
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import Control.Monad.Identity
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%default total
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||| a sequence of bindings under an existing context. each successive element
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||| has one more bound variable, which correspond to all previous elements
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||| as well as the surrounding context.
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public export
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data Telescope : (tm : Nat -> Type) -> (from, to : Nat) -> Type where
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Lin : Telescope tm from from
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(:<) : Telescope tm from to -> tm to -> Telescope tm from (S to)
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%name Telescope tel
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public export
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Telescope' : (a : Type) -> (from, to : Nat) -> Type
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Telescope' a = Telescope (\_ => a)
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||| a top level context is actually just a telescope over no existing bindings
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public export
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Context : (tm : Nat -> Type) -> (len : Nat) -> Type
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Context tm len = Telescope tm 0 len
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public export
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Context' : (a : Type) -> (len : Nat) -> Type
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Context' a = Context (\_ => a)
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public export
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tail : Context tm (S n) -> Context tm n
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tail (tel :< _) = tel
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export
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toSnocList : Telescope tm _ _ -> SnocList (Exists tm)
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toSnocList [<] = [<]
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toSnocList (tel :< t) = toSnocList tel :< Evidence _ t
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export %inline
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toList : Telescope tm _ _ -> List (Exists tm)
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toList tel = toListAcc tel [] where
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toListAcc : Telescope tm _ _ -> List (Exists tm) -> List (Exists tm)
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toListAcc [<] acc = acc
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toListAcc (tel :< t) acc = toListAcc tel (Evidence _ t :: acc)
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export %inline
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toSnocList' : Telescope' a _ _ -> SnocList a
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toSnocList' = map snd . toSnocList
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export %inline
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toList' : Telescope' a _ _ -> List a
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toList' = map snd . toList
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public export
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(.) : Telescope tm from mid -> Telescope tm mid to -> Telescope tm from to
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tel1 . [<] = tel1
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tel1 . (tel2 :< s) = (tel1 . tel2) :< s
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export
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(<><) : Telescope' a from to -> Vect n a -> Telescope' a from (n + to)
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(<><) tel [] = tel
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(<><) tel (x :: xs) {n = S n} =
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rewrite plusSuccRightSucc n to in
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(tel :< x) <>< xs
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public export
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getShiftWith : (forall from, to. tm from -> Shift from to -> tm to) ->
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Shift len out -> Context tm len -> Var len -> tm out
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getShiftWith shft by (ctx :< t) VZ = t `shft` ssDown by
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getShiftWith shft by (ctx :< t) (VS i) = getShiftWith shft (ssDown by) ctx i
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public export %inline
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getShift : CanShift tm => Shift len out -> Context tm len -> Var len -> tm out
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getShift = getShiftWith (//)
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public export %inline
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getWith : (forall from, to. tm from -> Shift from to -> tm to) ->
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Context tm len -> Var len -> tm len
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getWith shft = getShiftWith shft SZ
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infixl 8 !!
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public export %inline
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(!!) : CanShift tm => Context tm len -> Var len -> tm len
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(!!) = getWith (//)
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infixl 8 !!!
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public export %inline
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(!!!) : Context' tm len -> Var len -> tm
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(!!!) = getWith const
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public export
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find : Alternative f =>
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(forall n. tm n -> Bool) -> Context tm len -> f (Var len)
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find p [<] = empty
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find p (ctx :< x) = (guard (p x) $> VZ) <|> (VS <$> find p ctx)
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export
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0 telescopeLTE : Telescope _ from to -> from `LTE` to
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telescopeLTE [<] = reflexive
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telescopeLTE (tel :< _) = lteSuccRight $ telescopeLTE tel
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export
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(gt : from `GT` to) => Uninhabited (Telescope _ from to) where
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uninhabited tel = void $ LTEImpliesNotGT (telescopeLTE tel) gt
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export %hint
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0 succGT : S n `GT` n
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succGT = LTESucc reflexive
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parameters {auto _ : Applicative f}
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export
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traverse : (forall n. tm1 n -> f (tm2 n)) ->
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Telescope tm1 from to -> f (Telescope tm2 from to)
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traverse f [<] = pure [<]
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traverse f (tel :< x) = [|traverse f tel :< f x|]
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infixl 3 `app`
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||| like `(<*>)` but with effects
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export
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app : Telescope (\n => tm1 n -> f (tm2 n)) from to ->
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Telescope tm1 from to -> f (Telescope tm2 from to)
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app [<] [<] = pure [<]
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app (ftel :< f) (xtel :< x) = [|app ftel xtel :< f x|]
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app [<] (xtel :< _) = void $ uninhabited xtel
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app (ftel :< _) [<] = void $ uninhabited ftel
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export %inline
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sequence : Telescope (f . tm) from to -> f (Telescope tm from to)
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sequence = traverse id
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parameters {0 tm1, tm2 : Nat -> Type}
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(f : forall n. tm1 n -> tm2 n)
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export %inline
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map : Telescope tm1 from to -> Telescope tm2 from to
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map = runIdentity . traverse (pure . f)
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export %inline
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(<$>) : Telescope tm1 from to -> Telescope tm2 from to
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(<$>) = map
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export %inline
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(<*>) : Telescope (\n => tm1 n -> tm2 n) from to ->
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Telescope tm1 from to -> Telescope tm2 from to
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ftel <*> xtel = runIdentity $ (pure .) <$> ftel `app` xtel
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-- ...but can't write pure without `from,to` being ω, so no idiom brackets ☹
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export %inline
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(<$) : (forall n. tm1 n) -> Telescope tm2 from to -> Telescope tm1 from to
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x <$ tel = const x <$> tel
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export %inline
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zipWith : (forall n. tm1 n -> tm2 n -> tm3 n) ->
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Telescope tm1 from to -> Telescope tm2 from to ->
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Telescope tm3 from to
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zipWith f tel1 tel2 = f <$> tel1 <*> tel2
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export %inline
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zipWithLazy : forall tm1, tm2, tm3.
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(forall n. tm1 n -> tm2 n -> tm3 n) ->
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Telescope tm1 from to -> Telescope tm2 from to ->
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Telescope (\n => Lazy (tm3 n)) from to
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zipWithLazy f = zipWith $ delay .: f
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export
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lengthPrf : Telescope _ from to -> Subset Nat (\len => len + from = to)
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lengthPrf [<] = Element 0 Refl
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lengthPrf (tel :< _) =
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let len = lengthPrf tel in Element (S len.fst) (cong S len.snd)
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export
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lengthPrf0 : Context _ to -> Subset Nat (\len => len = to)
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lengthPrf0 ctx =
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let len = lengthPrf ctx in
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Element len.fst (rewrite sym $ plusZeroRightNeutral len.fst in len.snd)
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public export %inline
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length : Telescope {} -> Nat
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length = fst . lengthPrf
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export
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foldl : {0 acc : Nat -> Type} ->
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(f : forall n. acc n -> tm (n + from) -> acc (S n)) ->
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(z : acc 0) -> (tel : Telescope tm from to) -> acc (length tel)
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foldl f z [<] = z
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foldl f z (tel :< t) = f (foldl f z tel) (rewrite (lengthPrf tel).snd in t)
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export %inline
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foldMap : Monoid a => (forall n. tm n -> a) -> Telescope tm from to -> a
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foldMap f = foldl (\acc, tm => acc <+> f tm) neutral
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export %inline
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fold : Monoid a => Telescope' a from to -> a
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fold = foldMap id
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||| like `fold` but calculate the elements only when actually appending
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export %inline
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foldLazy : Monoid a => Telescope' (Lazy a) from to -> a
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foldLazy = foldMap force
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export %inline
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(forall n. Eq (tm n)) => Eq (Telescope tm from to) where
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(==) = foldLazy @{All} .: zipWithLazy (==)
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export %inline
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(forall n. Ord (tm n)) => Ord (Telescope tm from to) where
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compare = foldLazy .: zipWithLazy compare
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export %inline
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(forall n. Show (tm n)) => Show (Telescope tm from to) where
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showPrec d = showPrec d . toSnocList
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where Show (Exists tm) where showPrec d t = showPrec d t.snd
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export %inline
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(forall n. PrettyHL (tm n)) => PrettyHL (Telescope tm from to) where
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prettyM tel = separate (hl Delim ";") <$> traverse prettyM (toList tel)
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