代码语言：racket

所属分类：其他

代码描述：racket if for loop流程控制示例代码

代码标签： loop 流程 控制 示例

下面为部分代码预览，完整代码请点击下载或在bfwstudio webide中打开

#lang racket

(if #t               ; test expression
    "this is true"   ; then expression
    "this is false") ; else expression
; => "this is true"

;; In conditionals, all non-#f values are treated as true
(member 'Groucho '(Harpo Groucho Zeppo)) ; => '(Groucho Zeppo)
(if (member 'Groucho '(Harpo Groucho Zeppo))
    'yep
    'nope)
; => 'yep

;; `cond' chains a series of tests to select a result
(cond [(> 2 2) (error "wrong!")]
      [(< 2 2) (error "wrong again!")]
      [else 'ok]) ; => 'ok

;;; Pattern Matching

(define (fizzbuzz? n)
  (match (list (remainder n 3) (remainder n 5))
    [(list 0 0) 'fizzbuzz]
    [(list 0 _) 'fizz]
    [(list _ 0) 'buzz]
    [_          #f]))

(fizzbuzz? 15) ; => 'fizzbuzz
(fizzbuzz? 37) ; => #f

;;; Loops

;; Looping can be done through (tail-) recursion
(define (loop i)
  (when (< i 10)
    (printf "i=~a\n" i)
    (loop (add1 i))))
(loop 5) ; => i=5, i=6, ...

;; Similarly, with a named let
(let loop ((i 0))
  (when (< i 10)
    (printf "i=~a\n" i)
    (loop (add1 i)))) ; => i=0, i=1, ...

;; See below how to add a new `loop' form, but Racket already has a very
;; flexible `for' form for loops:
(for ([i 10])
  (printf "i=~a\n" i)) ; => i=0, i=1, ...
(for ([i (in-range 5 10)])
  (printf "i=~a\n" i)) ; => i=5, i=6, ...

;;; Iteration Over Other Sequences
;; `for' allows iteration over many other kinds of sequences:
;; lists, vectors, strings, sets, hash tables, etc...

(for ([i (in-list '(l i s t))])
  (displayln i))

(for ([i (in.........完整代码请登录后点击上方下载按钮下载查看

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