How to create a list with n applications of a procedure

问题

My question is related to this one but in my case I would like to obtain a list with the results of n applications of a function whose output is not computable again with the previous result (picking randomly an element from a list, for example).

That is, it is not the composition of a function n times with itself but the n results shown together into a list.

回答1:

Something like this?

#!racket/base
(require srfi/1)

(define (times/list proc n)
  (unfold-right zero? proc sub1 n))

(times/list (lambda (v) (abs (- v 5))) 10)
; ==> (4 3 2 1 0 1 2 3 4 5)

(times/list (lambda _ 5) 10)
; ==> (5 5 5 5 5 5 5 5 5 5)

(times/list (lambda _ (+ 1 (random 5))) 10)
; ==> (4 2 2 4 4 1 5 3 1 3) (varies)

回答2:

You can use for/list like this:

(define (times/list proc n)
  (for/list ([i n]) (proc)))

Using it:

> (times/list (λ () (random 5)) 10)
'(3 4 3 3 0 0 4 0 2 1)

来源：https://stackoverflow.com/questions/54024035/how-to-create-a-list-with-n-applications-of-a-procedure