Language/Symantic/Compiling/If.hs

   1 {-# LANGUAGE DataKinds #-}
   2 {-# LANGUAGE DefaultSignatures #-}
   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 {-# OPTIONS_GHC -fconstraint-solver-iterations=5 #-}
  14 -- | Symantic for @if@.
  15 module Language.Symantic.Compiling.If where
  16
  17 import Data.Monoid ((<>))
  18 import Data.Proxy
  19 import Data.String (IsString)
  20 import Data.Text (Text)
  21 import Data.Type.Equality ((:~:)(Refl))
  22
  23 import Language.Symantic.Typing
  24 import Language.Symantic.Compiling.Term
  25 import Language.Symantic.Compiling.Bool (tyBool)
  26 import Language.Symantic.Interpreting
  27 import Language.Symantic.Transforming.Trans
  28
  29 -- * Class 'Sym_If'
  30 class Sym_If term where
  31         if_ :: term Bool -> term a -> term a -> term a
  32         default if_ :: Trans t term => t term Bool -> t term a -> t term a -> t term a
  33         if_ = trans_map3 if_
  34
  35 -- * Type 'If'
  36 data If
  37 type instance Sym_of_Iface (Proxy If) = Sym_If
  38 type instance Consts_of_Iface (Proxy If) = Consts_imported_by If
  39 type instance Consts_imported_by If =
  40  '[ Proxy Bool
  41  ]
  42
  43 instance Sym_If HostI where
  44         if_ (HostI b) ok ko = if b then ok else ko
  45 instance Sym_If TextI where
  46         if_ (TextI cond) (TextI ok) (TextI ko) =
  47                 TextI $ \p v ->
  48                         let p' = Precedence 2 in
  49                         paren p p' $
  50                         "if " <> cond p' v <>
  51                         " then " <> ok p' v <>
  52                         " else " <> ko p' v
  53 instance (Sym_If r1, Sym_If r2) => Sym_If (DupI r1 r2) where
  54         if_  = dupI3 sym_If if_
  55
  56 instance Const_from Text cs => Const_from Text (Proxy If ': cs) where
  57         const_from s k = const_from s $ k . ConstS
  58
  59 instance -- If
  60  Proj_ConC cs (Proxy If)
  61 instance -- Term_fromI
  62  ( AST ast
  63  , Lexem ast ~ LamVarName
  64  , Inj_Const (Consts_of_Ifaces is) Bool
  65  , Term_from is ast
  66  ) => Term_fromI is (Proxy If) ast where
  67         term_fromI ast ctx k =
  68                 case ast_lexem ast of
  69                  "if" -> if_from
  70                  _ -> Left $ Error_Term_unsupported
  71                 where
  72                 if_from =
  73                  -- if :: Bool -> a -> a -> a
  74                         from_ast3 ast $ \ast_cond ast_ok ast_ko as ->
  75                         term_from ast_cond ctx $ \ty_cond (TermLC cond) ->
  76                         term_from ast_ok   ctx $ \ty_ok   (TermLC ok) ->
  77                         term_from ast_ko   ctx $ \ty_ko   (TermLC ko) ->
  78                         check_type (At Nothing tyBool) (At (Just ast_cond) ty_cond) $ \Refl ->
  79                         check_type (At (Just ast_ok) ty_ok) (At (Just ast_ko) ty_ko) $ \Refl ->
  80                         k as ty_ok $ TermLC $
  81                          \c -> if_ (cond c) (ok c) (ko c)
  82
  83 sym_If :: Proxy Sym_If
  84 sym_If = Proxy
  85
  86 syIf :: IsString a => Syntax a -> Syntax a -> Syntax a -> Syntax a
  87 syIf cond ok ko = Syntax "if" [cond, ok, ko]