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
|
{-# OPTIONS_GHC -dsuppress-all #-}
{-# LANGUAGE TemplateHaskell #-}
-- Testing example from the documentation
import Control.Applicative (liftA2)
import Test.Inspection
import ApNormalize
data Example a = Example a Bool [a] (Example a)
traverseNaive :: Applicative f => (a -> f b) -> Example a -> f (Example b)
traverseNaive go (Example a b c d) =
Example
<$> go a
<*> pure b
<*> traverse go c
<*> traverseNaive go d
-- Total: 1 <$>, 3 <*>
traverseAN :: Applicative f => (a -> f b) -> Example a -> f (Example b)
traverseAN go (Example a b c d) =
Example
<$>^ go a
<*> pure b
<*>^ traverse go c
<*>^ traverseAN go d
& lowerAps
-- Total: 1 <$>, 3 <*>
traverseNormal :: Applicative f => (a -> f b) -> Example a -> f (Example b)
traverseNormal go (Example a b c d) =
liftA2 (\a' -> Example a' b)
(go a)
(traverse go c)
<*> traverseNormal go d
-- Total: 1 liftA2, 1 <*>
traverseTree :: Applicative f => (a -> f b) -> Example a -> f (Example b)
traverseTree go (Example a b c d) =
(\((a', b'), (c', d')) -> Example a' b' c' d')
<$> ((,) <$> ((,) <$>^ go a
<*> pure b)
<*> ((,) <$>^ traverse go c
<*>^ traverseTree go d))
& lowerAps
-- 4 \<$\>, 3 \<*\>
inspect $ 'traverseNormal =/= 'traverseNaive
inspect $ 'traverseNormal === 'traverseAN
inspect $ 'traverseNormal === 'traverseTree
-- dummy
main :: IO ()
main = pure ()
|
