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Random Numbers in Racket
Here’s the translation of the Go code example to Racket, formatted in Markdown suitable for Hugo:
Our first example demonstrates generating random numbers in Racket. Here’s the full source code:
#lang racket
(require math/random)
(define (main)
; For example, `random` returns a random integer n,
; 0 <= n < 100.
(printf "~a,~a\n" (random 100) (random 100))
; `random` with no arguments returns a float f,
; 0.0 <= f < 1.0.
(printf "~a\n" (random))
; This can be used to generate random floats in
; other ranges, for example 5.0 <= f' < 10.0.
(printf "~a,~a\n"
(+ 5 (* (random) 5))
(+ 5 (* (random) 5)))
; If you want a known seed, use `pseudo-random-generator`.
; Create a new generator and use it with `parameterize`.
(define gen (make-pseudo-random-generator))
(pseudo-random-generator-vector-set! gen #(42 1024 1))
(parameterize ([current-pseudo-random-generator gen])
(printf "~a,~a\n" (random 100) (random 100)))
; Using the same seed produces the same sequence.
(define gen2 (make-pseudo-random-generator))
(pseudo-random-generator-vector-set! gen2 #(42 1024 1))
(parameterize ([current-pseudo-random-generator gen2])
(printf "~a,~a\n" (random 100) (random 100))))
(main)To run the program, save it as random-numbers.rkt and use racket:
$ racket random-numbers.rkt
68,56
0.8090228139659177
5.840125017402497,6.937056298890035
94,49
94,49Some of the generated numbers may be different when you run the sample.
In Racket, the math/random library provides functions for generating random numbers. The random function is versatile and can generate both integers and floating-point numbers.
When you need a known seed for reproducibility, Racket uses pseudo-random-generator objects. You can create a new generator, set its state, and use it within a parameterize block to affect the behavior of random.
See the Racket Random Number Generation documentation for references on other random quantities that Racket can provide.