Language/Symantic/Expr/Traversable.hs

   1 {-# LANGUAGE DefaultSignatures #-}
   2 {-# LANGUAGE GADTs #-}
   3 {-# LANGUAGE FlexibleContexts #-}
   4 {-# LANGUAGE FlexibleInstances #-}
   5 {-# LANGUAGE MultiParamTypeClasses #-}
   6 {-# LANGUAGE OverloadedStrings #-}
   7 {-# LANGUAGE Rank2Types #-}
   8 {-# LANGUAGE ScopedTypeVariables #-}
   9 {-# LANGUAGE TypeFamilies #-}
  10 {-# LANGUAGE TypeOperators #-}
  11 {-# LANGUAGE UndecidableInstances #-}
  12 {-# OPTIONS_GHC -fno-warn-orphans #-}
  13 -- | Expression for 'Traversable'.
  14 module Language.Symantic.Expr.Traversable where
  15
  16 import Control.Monad
  17 import Data.Traversable (Traversable)
  18 import qualified Data.Traversable as Traversable
  19 import Data.Proxy (Proxy(..))
  20 import Data.Type.Equality ((:~:)(Refl))
  21 import Prelude hiding (Traversable(..))
  22
  23 import Language.Symantic.Type
  24 import Language.Symantic.Repr
  25 import Language.Symantic.Expr.Root
  26 import Language.Symantic.Expr.Error
  27 import Language.Symantic.Expr.From
  28 import Language.Symantic.Expr.Lambda
  29 import Language.Symantic.Expr.Applicative
  30 import Language.Symantic.Trans.Common
  31
  32 -- * Class 'Sym_Traversable'
  33 -- | Symantic.
  34 class Sym_Applicative repr => Sym_Traversable repr where
  35         traverse :: (Traversable t, Applicative f)
  36          => repr ((->) a (f b)) -> repr (t a) -> repr (f (t b))
  37         default traverse :: (Trans tr repr, Traversable t, Applicative f)
  38          => tr repr ((->) a (f b)) -> tr repr (t a) -> tr repr (f (t b))
  39         traverse = trans_map2 traverse
  40 instance Sym_Traversable Repr_Host where
  41         traverse = liftM2 Traversable.traverse
  42 instance Sym_Traversable Repr_Text where
  43         traverse = repr_text_app2 "traverse"
  44 instance (Sym_Traversable r1, Sym_Traversable r2) => Sym_Traversable (Repr_Dup r1 r2) where
  45         traverse = repr_dup2 sym_Traversable traverse
  46
  47 sym_Traversable :: Proxy Sym_Traversable
  48 sym_Traversable = Proxy
  49
  50 -- * Type 'Expr_Traversable'
  51 -- | Expression.
  52 data Expr_Traversable (root:: *)
  53 type instance Root_of_Expr      (Expr_Traversable root)      = root
  54 type instance Type_of_Expr      (Expr_Traversable root)      = No_Type
  55 type instance Sym_of_Expr       (Expr_Traversable root) repr = Sym_Traversable repr
  56 type instance Error_of_Expr ast (Expr_Traversable root)      = No_Error_Expr
  57
  58 traverse_from
  59  :: forall root ty ast hs ret.
  60  ( ty ~ Type_Root_of_Expr (Expr_Traversable root)
  61  , Type0_Eq ty
  62  , Type1_Eq ty
  63  , Expr_From ast root
  64  , Type0_Lift   Type_Fun (Type_of_Expr root)
  65  , Type0_Unlift Type_Fun (Type_of_Expr root)
  66  , Type1_Unlift (Type_of_Expr root)
  67  , Error_Expr_Lift (Error_Expr (Error_of_Type ast ty) ty ast)
  68                    (Error_of_Expr ast root)
  69  , Root_of_Expr root ~ root
  70  , Type1_Constraint Applicative ty
  71  , Type1_Constraint Traversable ty
  72  ) => ast -> ast
  73  -> ExprFrom ast (Expr_Traversable root) hs ret
  74 traverse_from ast_g ast_ta ex ast ctx k =
  75  -- traverse :: (Traversable t, Applicative f) => (a -> f b) -> t a -> f (t b)
  76         expr_from (Proxy::Proxy root) ast_g ctx $
  77          \(ty_g::ty h_g) (Forall_Repr_with_Context g) ->
  78         expr_from (Proxy::Proxy root) ast_ta ctx $
  79          \ty_ta (Forall_Repr_with_Context ta) ->
  80
  81         check_type_fun ex ast ty_g $ \(Type2 Proxy ty_g_a ty_g_fb) ->
  82
  83         check_type1 ex ast ty_g_fb $ \(Type1 f ty_g_fb_b, Type1_Lift ty_f) ->
  84         check_type1 ex ast ty_ta $ \(Type1 t ty_ta_a, Type1_Lift ty_t) ->
  85
  86         check_type1_constraint ex (Proxy::Proxy Applicative) ast ty_g_fb $ \Dict ->
  87         check_type1_constraint ex (Proxy::Proxy Traversable) ast ty_ta $ \Dict ->
  88
  89         check_type0_eq ex ast ty_g_a ty_ta_a $ \Refl ->
  90
  91         k (
  92                 Type_Root $ ty_f $ Type1 f $
  93                 Type_Root $ ty_t $ Type1 t ty_g_fb_b
  94          ) $ Forall_Repr_with_Context $
  95          \c -> traverse (g c) (ta c)