是否有某种在Ruby中看不见的阵列终止？ [英] Is there some kind of unseen Array termination in Ruby?

问题描述

我写这需要阵列和COM presses可变长度并将它们转换为匹配数组长度的方法。

I am writing an method that takes variable lengths of arrays and compresses and converts them to matching array lengths.

的方法，接受从50至126的任意位置的阵列长度。 ..和调用时转换下来基于参数。这就意味着我动态访问在方法调用指定的范围。这也意味着我将访问，不会存在数组的索引。除了这一点，我访问范围可以是相等的。这是我的问题在于：它看起来与一系列访问时，数组的终止口袋行为古怪，而不是任何其他不存在的指数

The method accepts an array length of anywhere from 50 to 126 . .. and converts them down based on parameters when called. This means is I am dynamically accessing ranges that are specified at method call. This also means I will be accessing indices of the array that won't exist. In addition to this, the range I am accessing may be equal. This is where my problem lies: it appears that the terminating pocket of an array behaves strangely when accessing it with a range, as opposed to any other non-existent index

>> a = [0, 1, 2, 3, 4]
# => [0, 1, 2, 3, 4]  

>> a[5]
# => nil  

>> a[4..4]
# => [4]

>> a[6..6]
# => nil  

>> a[5..5]
# => [] <------GGRAAAAAhhh!!! Thought you were nil

>> a[5..7]
# => []   <-------you too

>> a[6..7]
# => nil <-----but you are behaving

有谁知道为什么出现这种情况？它针对我的code空数组一个额外的测试，但我的应用程序整天在我的rails追逐这个bug下来以后更加好奇。 FWIW我在Mac OS X，补丁级别114

Does anyone know why this happens? Its an extra test against an empty array for my code, but I am more curious after chasing this bug down in my rails app all day. FWIW I am running Ruby 1.8.6 on Mac OS X, patchlevel 114

推荐答案

在超出范围的范围选择是一个特殊情况，可以作为每文档：

The out-of range range selection is a special case, and works as per the docs:

http://www.ruby-doc.org/core/类/ Array.html＃M002183

虽然我会同意，它不是完全明显。

Though I'd agree that it's not exactly obvious.

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