Language/LOL/Symantic/Expr/If.hs

   1 {-# LANGUAGE DefaultSignatures #-}
   2 {-# LANGUAGE FlexibleContexts #-}
   3 {-# LANGUAGE FlexibleInstances #-}
   4 {-# LANGUAGE GADTs #-}
   5 {-# LANGUAGE MultiParamTypeClasses #-}
   6 {-# LANGUAGE OverloadedStrings #-}
   7 {-# LANGUAGE Rank2Types #-}
   8 {-# LANGUAGE ScopedTypeVariables #-}
   9 {-# LANGUAGE TypeFamilies #-}
  10 {-# LANGUAGE UndecidableInstances #-}
  11 module Language.LOL.Symantic.Expr.If where
  12
  13 import Data.Proxy (Proxy(..))
  14 import Data.Type.Equality ((:~:)(Refl))
  15 import Language.LOL.Symantic.AST
  16 import Language.LOL.Symantic.Expr.Bool
  17 import Language.LOL.Symantic.Expr.Common
  18 import Language.LOL.Symantic.Expr.Lambda
  19 import Language.LOL.Symantic.Repr.Dup
  20 import Language.LOL.Symantic.Trans.Common
  21 import Language.LOL.Symantic.Type
  22
  23 -- * Class 'Sym_If'
  24
  25 class Sym_If repr where
  26         if_   :: repr Bool -> repr a -> repr a -> repr a
  27         when_ :: repr Bool -> repr () -> repr ()
  28
  29         default if_   :: Trans t repr => t repr Bool -> t repr a -> t repr a -> t repr a
  30         default when_ :: Trans t repr => t repr Bool -> t repr () -> t repr ()
  31         if_   = trans_map3 if_
  32         when_ = trans_map2 when_
  33
  34 instance -- Sym_If Dup
  35  ( Sym_If r1
  36  , Sym_If r2
  37  ) => Sym_If (Dup r1 r2) where
  38         if_ (c1 `Dup` c2) (ok1 `Dup` ok2) (ko1 `Dup` ko2) =
  39                 if_ c1 ok1 ko1 `Dup`
  40                 if_ c2 ok2 ko2
  41         when_ (c1 `Dup` c2) (ok1 `Dup` ok2) =
  42                 when_ c1 ok1 `Dup`
  43                 when_ c2 ok2
  44
  45 -- * Type 'Expr_If'
  46 -- | Expression.
  47 data Expr_If (root:: *)
  48 type instance Root_of_Expr      (Expr_If root)      = root
  49 type instance Type_of_Expr      (Expr_If root)      = No_Type
  50 type instance Sym_of_Expr       (Expr_If root) repr = (Sym_If repr)
  51 type instance Error_of_Expr ast (Expr_If root)      = No_Error_Expr
  52
  53 instance -- Expr_from AST Expr_If
  54  ( Type_from AST (Type_Root_of_Expr root)
  55  , Expr_from AST root
  56  , Type_Root_Lift Type_Bool (Type_Root_of_Expr root)
  57  , Error_Expr_Lift (Error_Expr (Error_of_Type AST (Type_Root_of_Expr root))
  58                                (                   Type_Root_of_Expr root)
  59                                AST)
  60                    (Error_of_Expr AST root)
  61  , Root_of_Expr root ~ root
  62  , Implicit_HBool (Is_Last_Expr (Expr_If root) root)
  63  ) => Expr_from AST (Expr_If root) where
  64         expr_from px_ex ctx ast k =
  65                 case ast of
  66                  AST "if" asts ->
  67                         case asts of
  68                          [ast_cond, ast_ok, ast_ko] ->
  69                                 expr_from (Proxy::Proxy root) ctx ast_cond $
  70                                  \(ty_cond::Type_Root_of_Expr root h_n) (Forall_Repr_with_Context cond) ->
  71                                 expr_from (Proxy::Proxy root) ctx ast_ok $
  72                                  \(ty_ok::Type_Root_of_Expr root h_ok) (Forall_Repr_with_Context ok) ->
  73                                 expr_from (Proxy::Proxy root) ctx ast_ko $
  74                                  \(ty_ko::Type_Root_of_Expr root h_ko) (Forall_Repr_with_Context ko) ->
  75                                         when_type_eq px_ex ast
  76                                          type_bool ty_cond $ \Refl ->
  77                                                 when_type_eq px_ex ast
  78                                                  ty_ok ty_ko $ \Refl ->
  79                                                         k ty_ok $ Forall_Repr_with_Context $
  80                                                          \c -> if_ (cond c) (ok c) (ko c)
  81                          _ -> Left $ error_expr px_ex $
  82                                 Error_Expr_Wrong_number_of_arguments ast 3
  83                  _ -> Left $ error_expr_unsupported px_ex ast
  84
  85 -- ** Type 'Expr_Lambda_Bool_If'
  86 -- | Convenient alias.
  87 type Expr_Lambda_If_Bool lam
  88  =   Expr_Root (Expr_Alt (Expr_Lambda lam)
  89                          (Expr_Alt Expr_If
  90                                    Expr_Bool))
  91
  92 -- | Convenient alias around 'expr_from'.
  93 expr_lambda_if_bool_from
  94  :: forall lam ast root.
  95  ( Expr_from ast (Expr_Lambda_If_Bool lam)
  96  , root ~ Expr_Lambda_If_Bool lam
  97  ) => Proxy lam
  98  -> ast
  99  -> Either (Error_of_Expr ast root)
 100            (Exists_Type_and_Repr (Type_Root_of_Expr root)
 101                                  (Forall_Repr root))
 102 expr_lambda_if_bool_from _px_lam ast =
 103         expr_from
 104          (Proxy::Proxy root)
 105          Context_Empty ast $ \ty (Forall_Repr_with_Context repr) ->
 106                 Right $ Exists_Type_and_Repr ty $
 107                         Forall_Repr $ repr Context_Empty