使用高阶函数映射的字符串加密

Question

我写了下面的字符串加密代码。但我希望能够使用（读取）而不是使用硬编码值从键盘获取加密密钥。但我无法做到这一点，因为地图将列表作为参数。

#lang racket 

(define character-encryption 
    (lambda (ch) 
    (if (char-alphabetic? ch) 
     (character-rotation ch 3) 
     ch))) ; non-letter will not be encrypted. 

(define character-rotation 
    (lambda (ch num) 
    (integer->char (+ (char->integer ch) num)))) ; key=3 

(define string-encryption 
    (lambda (str) 
    (list->string (map character-encryption (string->list str))))) 

UPDATE

> (string-encryption (read)) 
"foo bar"      ; <- entered 
"irr edu"      ; output 

UPDATE

#lang racket 

(define character-encryption 
    (lambda (key) 
    (lambda (ch) 
     (if (char-alphabetic? ch) 
      (character-rotation ch key) 
      ch)))) ; non-letter will not be encrypted. 

(define character-rotation 
    (lambda (ch num) 
    (integer->char (+ (char->integer ch) num)))) ; key=3 (I want to read this number) 


(define string-encryption 
    (lambda (key str) 
    (list->string (map (character-encryption key) (string->list str))))) 

Answer 1

使用read-line读取线。结果是一个字符串。

更多在这里阅读： Docs on read-line