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Integrate types to the module system.
[haskell/symantic.git] / symantic-lib / Language / Symantic / Lib / If.hs
1 {-# LANGUAGE UndecidableInstances #-}
2 {-# OPTIONS_GHC -fno-warn-orphans #-}
3 -- | Symantic for @If@.
4 module Language.Symantic.Lib.If where
5
6 import qualified Data.Text as Text
7
8 import Language.Symantic
9 import Language.Symantic.Lib.Bool (tyBool)
10 import Language.Symantic.Lib.Function (a0)
11
12 -- * Type 'If'
13 data If
14
15 -- * Class 'Sym_If'
16 type instance Sym If = Sym_If
17 class Sym_If term where
18 if_ :: term Bool -> term a -> term a -> term a
19 default if_ :: Sym_If (UnT term) => Trans term => term Bool -> term a -> term a -> term a
20 if_ = trans3 if_
21
22 -- Interpreting
23 instance Sym_If Eval where
24 if_ (Eval b) ok ko = if b then ok else ko
25 instance Sym_If View where
26 if_ (View cond) (View ok) (View ko) =
27 View $ \po v ->
28 parenInfix po op $
29 Text.concat
30 [ "if ", cond (op, SideL) v
31 , " then ", ok (op, SideL) v
32 , " else ", ko (op, SideL) v ]
33 where op = infixN 2
34 instance (Sym_If r1, Sym_If r2) => Sym_If (Dup r1 r2) where
35 if_ = dup3 @Sym_If if_
36
37 -- Transforming
38 instance (Sym_If term, Sym_Lambda term) => Sym_If (BetaT term)
39
40 -- Typing
41 instance NameTyOf If where
42 nameTyOf _c = ["If"] `Mod` "If"
43 instance ClassInstancesFor If
44 instance TypeInstancesFor If
45
46 -- Compiling
47 instance Gram_Term_AtomsFor src ss g If
48 -- TODO: some support for if-then-else or ternary (?:) operator
49 instance ModuleFor src ss If
50
51 -- ** 'Type's
52
53 -- ** 'Term's
54 teIf_if :: TermDef If '[Proxy a] (() #> (Bool -> a -> a -> a))
55 teIf_if = Term noConstraint (tyBool ~> a0 ~> a0 ~> a0) $ teSym @If $ lam3 if_