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utils: Add in-random.

This commit is contained in:
Sergiu Ivanov 2020-03-20 01:19:14 +01:00
parent f09f24d2dd
commit 9502a9e981
2 changed files with 46 additions and 1 deletions
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19
utils-tests.rkt
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@ -129,3 +129,22 @@
(test-case "Functions"
(check-true (procedure-fixed-arity? not))
(check-false (procedure-fixed-arity? +)))
(test-case "Randomness"
(begin
(random-seed 0)
(check-equal? (stream->list (stream-take (in-random 100) 10))
'(85 65 20 40 89 45 54 38 26 62))
(check-equal? (stream->list (stream-take (in-random 50 100) 10))
'(75 59 82 85 61 85 59 64 75 53))
(check-equal? (stream->list (stream-take (in-random) 10))
'(0.1656109603231493
0.9680391127132195
0.051518813640790355
0.755901955353936
0.5923534604277275
0.5513340634474264
0.7022057040731392
0.48375400938578744
0.7538961707172924
0.01828428516237329))))

28
utils.rkt
View File

@ -33,7 +33,11 @@
[collect-by-key/sets (-> (listof any/c) (listof any/c) (values (listof any/c) (listof (set/c any/c))))]
[ht-values/list->set (-> (hash/c any/c (listof any/c)) (hash/c any/c (set/c any/c)))]
[procedure-fixed-arity? (-> procedure? boolean?)])
[procedure-fixed-arity? (-> procedure? boolean?)]
[in-random (case-> (-> (stream/c (and/c real? inexact? (>/c 0) (</c 1))))
(-> (integer-in 1 4294967087) (stream/c exact-nonnegative-integer?))
(-> exact-integer? (integer-in 1 4294967087)
(stream/c exact-nonnegative-integer?)))])
;; Contracts
(contract-out [variable-mapping? contract?]
[string-variable-mapping? contract?]
@ -329,3 +333,25 @@
(define (procedure-fixed-arity? func)
(match (procedure-arity func)
[(arity-at-least _) #f] [arity #t]))
;;; ==========
;;; Randomness
;;; ==========
;;; Generates a stream of inexact random numbers. The meaning of the
;;; arguments is the same as for the function random:
;;;
;;; (in-randoms k) — a sequence of random exact integers in the range
;;; 0 to k-1.
;;;
;;; (in-randoms min max) — a sequence of random exact integers the
;;; range min to max-1.
;;;
;;; (in-randoms) — a sequence of random inexact numbers between
;;; 0 and 1.
(define in-random
(case-lambda
[() (for/stream ([i (in-naturals)]) (random))]
[(k) (for/stream ([i (in-naturals)]) (random k))]
[(min max) (for/stream ([i (in-naturals)]) (random min max))]))