blob: 95d60b555db0dc7c722265a6fce2689316bc528d (
plain)
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
|
(.module:
[lux #*
[control
functor
monad
comonad
["." continuation (#+ pending Cont)]
["p" parser]]
[macro (#+ with-gensyms)
["." code]
["s" syntax (#+ syntax: Syntax)]]
[data
bit
[collection
[list ("list/." Monad<List>)]]]])
## [Types]
(type: #export (Sequence a)
{#.doc "An infinite sequence of values."}
(Cont [a (Sequence a)]))
## [Utils]
(def: (cycle' x xs init full)
(All [a]
(-> a (List a) a (List a) (Sequence a)))
(case xs
#.Nil (pending [x (cycle' init full init full)])
(#.Cons x' xs') (pending [x (cycle' x' xs' init full)])))
## [Functions]
(def: #export (iterate f x)
{#.doc "Create a sequence by applying a function to a value, and to its result, on and on..."}
(All [a]
(-> (-> a a) a (Sequence a)))
(pending [x (iterate f (f x))]))
(def: #export (repeat x)
{#.doc "Repeat a value forever."}
(All [a]
(-> a (Sequence a)))
(pending [x (repeat x)]))
(def: #export (cycle xs)
{#.doc "Go over the elements of a list forever.
The list should not be empty."}
(All [a]
(-> (List a) (Maybe (Sequence a))))
(case xs
#.Nil #.None
(#.Cons x xs') (#.Some (cycle' x xs' x xs'))))
(do-template [<name> <return> <part>]
[(def: #export (<name> s)
(All [a] (-> (Sequence a) <return>))
(let [[h t] (continuation.run s)]
<part>))]
[head a h]
[tail (Sequence a) t])
(def: #export (nth idx s)
(All [a] (-> Nat (Sequence a) a))
(let [[h t] (continuation.run s)]
(if (n/> |0 idx)
(nth (dec idx) t)
h)))
(do-template [<taker> <dropper> <splitter> <pred-type> <pred-test> <pred-step>]
[(def: #export (<taker> pred xs)
(All [a]
(-> <pred-type> (Sequence a) (List a)))
(let [[x xs'] (continuation.run xs)]
(if <pred-test>
(list& x (<taker> <pred-step> xs'))
(list))))
(def: #export (<dropper> pred xs)
(All [a]
(-> <pred-type> (Sequence a) (Sequence a)))
(let [[x xs'] (continuation.run xs)]
(if <pred-test>
(<dropper> <pred-step> xs')
xs)))
(def: #export (<splitter> pred xs)
(All [a]
(-> <pred-type> (Sequence a) [(List a) (Sequence a)]))
(let [[x xs'] (continuation.run xs)]
(if <pred-test>
(let [[tail next] (<splitter> <pred-step> xs')]
[(#.Cons [x tail]) next])
[(list) xs])))]
[take-while drop-while split-while (-> a Bit) (pred x) pred]
[take drop split Nat (n/> |0 pred) (dec pred)]
)
(def: #export (unfold step init)
{#.doc "A stateful way of infinitely calculating the values of a sequence."}
(All [a b]
(-> (-> a [a b]) a (Sequence b)))
(let [[next x] (step init)]
(pending [x (unfold step next)])))
(def: #export (filter p xs)
(All [a] (-> (-> a Bit) (Sequence a) (Sequence a)))
(let [[x xs'] (continuation.run xs)]
(if (p x)
(pending [x (filter p xs')])
(filter p xs'))))
(def: #export (partition p xs)
{#.doc "Split a sequence in two based on a predicate.
The left side contains all entries for which the predicate is #1.
The right side contains all entries for which the predicate is #0."}
(All [a] (-> (-> a Bit) (Sequence a) [(Sequence a) (Sequence a)]))
[(filter p xs) (filter (complement p) xs)])
## [Structures]
(structure: #export _ (Functor Sequence)
(def: (map f fa)
(let [[h t] (continuation.run fa)]
(pending [(f h) (map f t)]))))
(structure: #export _ (CoMonad Sequence)
(def: functor Functor<Sequence>)
(def: unwrap head)
(def: (split wa)
(let [[head tail] (continuation.run wa)]
(pending [wa (split tail)]))))
## [Pattern-matching]
(syntax: #export (^sequence& {patterns (s.form (p.many s.any))}
body
{branches (p.some s.any)})
{#.doc (doc "Allows destructuring of sequences in pattern-matching expressions."
"Caveat emptor: Only use it for destructuring, and not for testing values within the sequences."
(let [(^sequence& x y z _tail) (some-sequence-func 1 2 3)]
(func x y z)))}
(with-gensyms [g!sequence]
(let [body+ (` (let [(~+ (list/join (list/map (function (_ pattern)
(list (` [(~ pattern) (~ g!sequence)])
(` ((~! continuation.run) (~ g!sequence)))))
patterns)))]
(~ body)))]
(wrap (list& g!sequence body+ branches)))))
|
