gistfile1.rkt

#lang racket

(require rackunit)

;; int -> string
(define (line n)
  (list->string (build-list n (λ (x) #\*))))

(check-equal? (line 3) "***")
(check-equal? (line 1) "*")

;; listof<int> -> string
(define (histogram lst)
  (apply string-append
         (for/list ([i lst])
           (string-append (line i) "\n"))))

(check-equal? (histogram '(1 2)) "*\n**\n")

(display (histogram '(1 2 3)))