为什么在Ruby中无法使用直到的用法，而在另一种用法却无法使用呢? [英] Why does this usage of until in Ruby not work, while another usage does?

问题描述

下面的代码给出了错误:

The code below gives an error:

def bubble_sort(arr)
  until arr == arr.sort do
    (arr.count - 1).times do |i|
      (arr[i], arr[i + 1] = arr[i + 1], arr[i]) if (arr[i] > arr[i + 1])
    end
  end 

  arr
end

(eval):433:(eval):433:编译错误(SyntaxError)

(eval):433: (eval):433: compile error (SyntaxError)

(eval):426:语法错误，意外的kDO_COND，预期为kEND (arr.count-1).times做| i | ^

(eval):426: syntax error, unexpected kDO_COND, expecting kEND (arr.count - 1).times do |i| ^

(eval):433:语法错误，意外的kEND，期望$ end

(eval):433: syntax error, unexpected kEND, expecting $end

但是下面的另一个变体成功通过了.为什么?

But another variation of it below passes successfully. Why?

def bubble_sort(arr)
  begin
    (arr.count - 1).times do |i|
      (arr[i], arr[i + 1] = arr[i + 1], arr[i]) if (arr[i] > arr[i + 1])
    end
  end until arr == arr.sort

  arr
end

推荐答案

经过一些调试，这看上去像是1.8.7(labs.codecademy.com使用的版本)中irb中的错误.在本地安装Ruby 1.8.7-p374时，我看到的是同一件事.但是，如果我将代码作为普通的Ruby文件运行，则可以正常工作.

After a bit of debugging, this looks like a bug in irb on 1.8.7 (the version that labs.codecademy.com uses). Locally, when installing Ruby 1.8.7-p374 I see the same thing. However, if I run the code as a normal Ruby file, it works just fine.

但是，Ruby 1.8.7是

However, Ruby 1.8.7 is officially retired, and it seems to me like the Codecademy Labs site is no longer maintained, either, so I recommend either learning Ruby with the "full" Codecademy site, or installing a more recent version of Ruby (I recommend 2.0.0) locally.

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