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
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
|
{-# LANGUAGE ScopedTypeVariables, ExistentialQuantification, ApplicativeDo #-}
module Main where
import Control.Applicative
import Text.PrettyPrint
(a:b:c:d:e:f:g:h:_) = map (\c -> doc [c]) ['a'..]
-- a | b
test1 :: M ()
test1 = do
x1 <- a
x2 <- b
const (return ()) (x1,x2)
-- no parallelism
test2 :: M ()
test2 = do
x1 <- a
x2 <- const g x1
const (return ()) (x1,x2)
-- a | (b;g) | e
test3 :: M ()
test3 = do
x1 <- a
x2 <- b
x3 <- const g x2
x4 <- e
return () `const` (x1,x2,x3,x4)
-- (a ; (b | g)) | c
-- or
-- ((a | b); g) | c
test4 :: M ()
test4 = do
x1 <- a
x2 <- b
x3 <- const g x1
x4 <- c
return () `const` (x2,x3,x4)
-- (a | b | c); (g | h)
test5 :: M ()
test5 = do
x1 <- a
x2 <- b
x3 <- c
x4 <- const g x1
x5 <- const h x3
return () `const` (x3,x4,x5)
-- b/c in parallel, e/f in parallel
-- a; (b | (c; (d; (e | (f; g)))))
test6 :: M ()
test6 = do
x1 <- a
x2 <- const b x1
x3 <- const c x1
x4 <- const d x3
x5 <- const e x4
x6 <- const f x4
x7 <- const g x6
return () `const` (x1,x2,x3,x4,x5,x6,x7)
-- (a | b); (c | d)
test7 :: M ()
test7 = do
x1 <- a
x2 <- b
x3 <- const c x1
x4 <- const d x2
return () `const` (x3,x4)
-- a; (b | c | d)
--
-- alternative (but less good):
-- ((a;b) | c); d
test8 :: M ()
test8 = do
x1 <- a
x2 <- const b x1
x3 <- c
x4 <- const d x1
return () `const` (x2,x3,x4)
-- test that Lets don't get in the way
-- ((a | (b; c)) | d) | e
test9 :: M ()
test9 = do
x1 <- a
let x = doc "x" -- this shouldn't get in the way of grouping a/b
x2 <- b
x3 <- const c x2
x4 <- d
x5 <- e
let y = doc "y"
return ()
-- ((a | b) ; (c | d)) | e
test10 :: M ()
test10 = do
x1 <- a
x2 <- b
let z1 = (x1,x2)
x3 <- const c x1
let z2 = (x1,x2)
x4 <- const d z1
x5 <- e
return (const () (x3,x4,x5))
main = mapM_ run
[ test1
, test2
, test3
, test4
, test5
, test6
, test7
, test8
, test9
, test10
]
-- Testing code, prints out the structure of a monad/applicative expression
newtype M a = M (Bool -> (Maybe Doc, a))
maybeParen True d = parens d
maybeParen _ d = d
run :: M a -> IO ()
run (M m) = print d where (Just d,_) = m False
instance Functor M where
fmap f m = m >>= return . f
instance Applicative M where
pure a = M $ \_ -> (Nothing, a)
M f <*> M a = M $ \p ->
let (Just d1, f') = f True
(Just d2, a') = a True
in
(Just (maybeParen p (d1 <+> char '|' <+> d2)), f' a')
instance Monad M where
return = pure
M m >>= k = M $ \p ->
let (d1, a) = m True
(d2, b) = case k a of M f -> f True
in
case (d1,d2) of
(Nothing,Nothing) -> (Nothing, b)
(Just d, Nothing) -> (Just d, b)
(Nothing, Just d) -> (Just d, b)
(Just d1, Just d2) -> (Just (maybeParen p (d1 <> semi <+> d2)), b)
doc :: String -> M ()
doc d = M $ \_ -> (Just (text d), ())
|
