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
160
161
162
163
164
165
166
167
168
|
{-# LANGUAGE CPP #-}
{-# LANGUAGE FlexibleInstances #-}
-----------------------------------------------------------------------------
-- |
-- Module : Control.Arrow.Transformer.Static
-- Copyright : (c) Ross Paterson 2003
-- License : BSD-style (see the LICENSE file in the distribution)
--
-- Maintainer : R.Paterson@city.ac.uk
-- Stability : experimental
-- Portability : non-portable (multi-parameter type classes)
--
-- Arrow transformer adding static information.
module Control.Arrow.Transformer.Static(
StaticArrow(StaticArrow), StaticMonadArrow, StaticArrowArrow,
wrap, unwrap, wrapA, unwrapA, wrapM, unwrapM,
) where
import Control.Arrow.Internals
import Control.Arrow.Operations
import Control.Arrow.Transformer
import Control.Applicative
import Control.Arrow
import Control.Category
import Control.Monad
import Data.Monoid
#if (MIN_VERSION_base(4,9,0)) && !(MIN_VERSION_base(4,11,0))
import Data.Semigroup
#endif
import Prelude hiding (id,(.))
-- | An arrow type that augments the underlying arrow with static information.
newtype StaticArrow f a b c = StaticArrow (f (a b c))
instance (Arrow a, Applicative f) => ArrowTransformer (StaticArrow f) a where
lift f = StaticArrow (pure f)
instance (Category a, Applicative f) => Category (StaticArrow f a) where
id = StaticArrow (pure id)
StaticArrow f . StaticArrow g = StaticArrow ((.) <$> f <*> g)
instance (Arrow a, Applicative f) => Arrow (StaticArrow f a) where
arr f = StaticArrow (pure (arr f))
first (StaticArrow f) = StaticArrow (first <$> f)
-- The following promotions follow directly from the arrow transformer.
instance (ArrowZero a, Applicative f) => ArrowZero (StaticArrow f a) where
zeroArrow = lift zeroArrow
instance (ArrowCircuit a, Applicative f) => ArrowCircuit (StaticArrow f a) where
delay x = lift (delay x)
instance (ArrowError ex a, Applicative f) => ArrowError ex (StaticArrow f a) where
raise = lift raise
handle (StaticArrow f) (StaticArrow h) =
StaticArrow (handle <$> f <*> h)
tryInUnless (StaticArrow f) (StaticArrow s) (StaticArrow h) =
StaticArrow (tryInUnless <$> f <*> s <*> h)
instance (ArrowReader r a, Applicative f) => ArrowReader r (StaticArrow f a) where
readState = lift readState
newReader (StaticArrow f) = StaticArrow (newReader <$> f)
instance (ArrowState s a, Applicative f) => ArrowState s (StaticArrow f a) where
fetch = lift fetch
store = lift store
instance (ArrowWriter w a, Applicative f) => ArrowWriter w (StaticArrow f a) where
write = lift write
newWriter (StaticArrow f) = StaticArrow (newWriter <$> f)
-- Classes that are preserved.
instance (ArrowChoice a, Applicative f) => ArrowChoice (StaticArrow f a) where
left (StaticArrow f) = StaticArrow (left <$> f)
-- ArrowApply is generally not preserved.
instance (ArrowLoop a, Applicative f) => ArrowLoop (StaticArrow f a) where
loop (StaticArrow f) = StaticArrow (loop <$> f)
instance (ArrowPlus a, Applicative f) => ArrowPlus (StaticArrow f a) where
StaticArrow f <+> StaticArrow g = StaticArrow ((<+>) <$> f <*> g)
-- Other instances
instance (Arrow a, Applicative f) => Functor (StaticArrow f a b) where
fmap f g = g >>> arr f
instance (Arrow a, Applicative f) => Applicative (StaticArrow f a b) where
pure x = arr (const x)
f <*> g = f &&& g >>> arr (uncurry id)
instance (ArrowPlus a, Applicative f) => Alternative (StaticArrow f a b) where
empty = zeroArrow
f <|> g = f <+> g
#if MIN_VERSION_base(4,9,0)
instance (ArrowPlus a, Applicative f) => Semigroup (StaticArrow f a b c) where
(<>) = (<+>)
#endif
instance (ArrowPlus a, Applicative f) => Monoid (StaticArrow f a b c) where
mempty = zeroArrow
#if !(MIN_VERSION_base(4,11,0))
mappend = (<+>)
#endif
-- promotions
instance (ArrowAddStream a a', Applicative f) =>
ArrowAddStream (StaticArrow f a) (StaticArrow f a') where
liftStream (StaticArrow f) = StaticArrow (liftStream <$> f)
elimStream (StaticArrow f) = StaticArrow (elimStream <$> f)
instance (ArrowAddState s a a', Applicative f) =>
ArrowAddState s (StaticArrow f a) (StaticArrow f a') where
liftState (StaticArrow f) = StaticArrow (liftState <$> f)
elimState (StaticArrow f) = StaticArrow (elimState <$> f)
instance (ArrowAddReader r a a', Applicative f) =>
ArrowAddReader r (StaticArrow f a) (StaticArrow f a') where
liftReader (StaticArrow f) = StaticArrow (liftReader <$> f)
elimReader (StaticArrow f) = StaticArrow (elimReader <$> f)
instance (ArrowAddWriter w a a', Applicative f) =>
ArrowAddWriter w (StaticArrow f a) (StaticArrow f a') where
liftWriter (StaticArrow f) = StaticArrow (liftWriter <$> f)
elimWriter (StaticArrow f) = StaticArrow (elimWriter <$> f)
instance (ArrowAddError ex a a', Applicative f) =>
ArrowAddError ex (StaticArrow f a) (StaticArrow f a') where
liftError (StaticArrow f) = StaticArrow (liftError <$> f)
elimError (StaticArrow f) (StaticArrow h) =
StaticArrow (elimError <$> f <*> h)
wrap :: (Applicative f, Arrow a) => f (a b c) -> StaticArrow f a b c
wrap = StaticArrow
unwrap :: (Applicative f, Arrow a) => StaticArrow f a b c -> f (a b c)
unwrap (StaticArrow f) = f
-- | A special case.
type StaticArrowArrow a s = StaticArrow (WrappedArrow a s)
wrapA :: (Arrow a, Arrow a') => a s (a' b c) -> StaticArrowArrow a s a' b c
wrapA x = StaticArrow (WrapArrow x)
unwrapA :: (Arrow a, Arrow a') => StaticArrowArrow a s a' b c -> a s (a' b c)
unwrapA (StaticArrow (WrapArrow x)) = x
-- | A special case is monads applied to the whole arrow, in contrast to
-- 'Kleisli' arrows, in which the monad is applied to the output.
type StaticMonadArrow m = StaticArrow (WrappedMonad m)
wrapM :: (Monad m, Arrow a) => m (a b c) -> StaticMonadArrow m a b c
wrapM x = StaticArrow (WrapMonad x)
unwrapM :: (Monad m, Arrow a) => StaticMonadArrow m a b c -> m (a b c)
unwrapM (StaticArrow (WrapMonad x)) = x
|
