遍历 Racket 中的字母 [英] Iterate through the letters of the alphabet in Racket

问题描述

我想编写一个程序，将字母表中的字母作为符号进行迭代，并对它们进行处理.我希望它大致相当于这个 C 代码:

I'd like to write a program that iterates through the letters in the alphabet as symbols and does something with them. I'd like it to be roughly equivalent to this C code:

for(char letter = 'a'; letter <= 'z'; letter++)
{
    printf("The letter is %c\n", letter);
}

我真的不知道如何在 Racket 中做到这一点.感谢您的帮助.

I really have no idea how to do this in Racket. Thanks for your help.

推荐答案

假设您只想迭代小写英文字母，这里有一种方法:

Assuming that you only want to iterate over lowercase English alphabet letters, here's one way to do it:

(define alphabet (string->list "abcdefghijklmnopqrstuvwxyz"))

(for ([letter alphabet])
  (displayln letter))

你可以用 for 循环做更多的事情.例如，

You can do a lot more with for loops though. For example,

(for/list ([let alphabet] [r-let (reverse alphabet)])
  (list let r-let))

生成一个字母列表，与另一个方向的字母配对.虽然这实际上用地图表示更好:(map list letter (reverse letters)).

produces a list of letters paired with letters going the other direction. Although that's actually better expressed as a map: (map list alphabet (reverse alphabet)).

此外，SRFI-14 提供了更多操作如果您需要更多字符集.

Also, SRFI-14 provides more operations over sets of characters if you need more.

最初，我用 char->integer、integer->char 和 range 做了一些事情，但我有现在更简单了.

Originally, I did something with char->integer, integer->char, and range but what I have now is simpler.

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