quox/lib/Quox/Context.idr
2023-03-13 18:25:07 +01:00

231 lines
6.7 KiB
Idris

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