Question

How do I generate random in Scheme? Is there a special form or would I have to create a procedure? And if so, how do I do that? (I’m trying to create a procedure called random-choice that inputs two strategies and returns one at random.)

Answer 1

The procedure is called, surprisingly enough, random – although the exact syntax might be different depending on the Scheme interpreter in use (read the documentation!), but the general idea is as follows:

(random)
=> 0.9113789707345018

For returning one of two possible values, this will do the trick in Racket:

(define (random-choice a b)
  (if (zero? (random 2)) a b))

Notice that the 2 argument passed to random forces it to randomly return one of two possible values: 0 or 1. So if (random 2) evaluates to 0 then a is returned, otherwise b is returned.

(random-choice 4 2)
=> 4
(random-choice 4 2)
=> 2