1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
|
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE DuplicateRecordFields #-}
{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE TypeApplications #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE FlexibleContexts #-}
-- Note: this file may contain spoilers
-- (although I would be really surprised if it did, I haven't seen the films)
module StarWars where
import GHC.Generics
import Data.Generics.Product
data Episode = NEWHOPE | EMPIRE | JEDI
deriving (Generic, Show, Eq)
data Character = Character
{ name :: String
, friends :: [Character]
, appearsIn :: [Episode]
} deriving (Generic, Show, Eq)
data Human = Human
{ name :: String
, friends :: [Character]
, appearsIn :: [Episode]
, homePlanet :: String
} deriving (Generic, Show)
data Droid = Droid
{ friends :: [Character]
, appearsIn :: [Episode]
, name :: String
, primaryFunction :: String
} deriving (Generic, Show)
luke :: Human
luke = Human
{ name = "Luke Skywalker"
, friends = []
, appearsIn = [NEWHOPE, EMPIRE, JEDI]
, homePlanet = "Saturn (?)"
}
r2d2 :: Droid
r2d2 = Droid
{ name = "R2-D2"
, friends = [upcast luke]
, appearsIn = [NEWHOPE, EMPIRE, JEDI]
, primaryFunction = "repair ships"
}
c3po :: Droid
c3po = Droid
{ name = "C3PO"
, friends = [upcast r2d2, upcast luke]
, appearsIn = [NEWHOPE, EMPIRE, JEDI]
, primaryFunction = "protocol and human relations"
}
getName :: HasField' "name" r a => r -> a
getName = getField @"name"
-- upcast :: Subtype a b => a -> b
characters :: [Character]
characters = [upcast r2d2, upcast luke, upcast c3po]
names :: [String]
names = map getName characters
-- => ["R2-D2","Luke Skywalker","C3PO"]
|
