blob: cc19f2c4f56d6c8a1f324b898dac34df23b32687 (
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
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;
;; Stream application examples
;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(ns clojure.contrib.stream-utils.examples
(:use [clojure.contrib.stream-utils
:only (defst-seq defst-gen pick pick-all stream-as-seq)])
(:use [clojure.contrib.monads :only (domonad)]))
; Transform a stream of numbers into a stream of sums of
; two consecutive numbers.
(defst-seq sum-two [] [xs]
(domonad
[x1 (pick xs)
x2 (pick xs)]
(+ x1 x2)))
(sum-two '(1 2 3 4 5 6 7 8))
; The same example, but with a generator interface for the output stream
(defst-gen sum-two-gen [] [xs]
(domonad
[x1 (pick xs)
x2 (pick xs)]
(+ x1 x2)))
(def g (sum-two-gen '(1 2 3 4 5 6 7 8)))
(let [[v1 g] (g :eos)]
(let [[v2 g] (g :eos)]
(let [[v3 g] (g :eos)]
(let [[v4 g] (g :eos)]
(let [[v5 g] (g :eos)]
[v1 v2 v3 v4 v5])))))
; Map (for a single stream) written as a stream transformer
(defst-seq my-map-1 [f] [xs]
(domonad
[x (pick xs)]
(f x)))
(my-map-1 inc [1 2 3])
; Map for two stream arguments
(defst-seq my-map-2 [f] [xs ys]
(domonad
[x (pick xs)
y (pick ys)]
(f x y)))
(my-map-2 + '(1 2 3 4) '(10 20 30 40))
; Map for any number of stream arguments
(defst-seq my-map [f] [& streams]
(domonad
[vs pick-all]
(apply f vs)))
(my-map inc [1 2 3])
(my-map + '(1 2 3 4) '(10 20 30 40))
; Filter written as a stream transformer
(defst-seq my-filter [p] [xs]
(domonad
[x (pick xs) :when (p x)]
x))
(my-filter odd? [1 2 3])
; A simple random number generator, implemented as a generator function
(defn rng [seed]
(fn [eos]
(let [m 259200
value (/ (float seed) (float m))
next (rem (+ 54773 (* 7141 seed)) m)]
[value (rng next)])))
(take 10 (stream-as-seq (rng 1)))
|
