在PLT方案中循环 [英] Loop in PLT Scheme

问题描述

如何像在Java-

for(int i=0;i<10;){
     for(int j=0;j<3;){
          System.out.println(""+j);
          j++;
     }
      System.out.println(""+i);
      i++;
}

推荐答案

您在Java中的示例仅通过学习一些新关键字就不会直接映射到Scheme语言，因为没有显式构造可在其中实现for循环方案(除非您自己编写一个构造！).在Scheme中，完成此操作的方法是定义一个遍历列表的递归函数.这是一个如何在Scheme中执行for循环样式函数的示例:

Your example in Java doesn't directly map onto the Scheme language by just learning a few new keywords as there aren't explicit constructs for implementing a for loop in Scheme (unless you write a construct yourself!). The cookbook way to do this in Scheme is to define a recursive function that loops over a list. Here's an example of how to do a for-loop style function in Scheme:

(define (doit x x-max dx)
  (if (<= x x-max)
    (begin
      ;;...perform loop body with x...
      (doit (+ x dx) x-max dx))))

(doit a b dx) ; execute loop from a to b in steps of dx

从此页面拍摄:

指南和计划链接

这是指向页面的另一个链接，该页面描述了将循环从命令式语言转换为Scheme时需要理解的思想:

Here's another link to a page that describes the ideas you need to understand to translate loops from imperative languages to Scheme:

方案循环构造

方案是一种非常有趣的语言，您还应该阅读计算机程序的结构和解释，这是麻省理工学院以前用于教学计划的教科书.

Scheme is a really interesting language to learn, you should also read the Structure and Interpretation of Computer Programs, which is the textbook formerly used for teaching Scheme at MIT.

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