From: Heesob Park <phasis@...>
Date: 2013-01-08T22:09:43+09:00
Subject: Re: ruby 1.9.3p362 ranges as conditions bug?

Hi,

2013/1/8 tamouse mailing lists <tamouse.lists@gmail.com>:
> On Mon, Jan 7, 2013 at 12:01 AM, Matma Rex <matma.rex@gmail.com> wrote:
>> On Mon, 07 Jan 2013 05:26:43 +0100, tamouse mailing lists
>> <tamouse.lists@gmail.com> wrote:
>>
>>> On Sun, Jan 6, 2013 at 9:09 PM, windwiny <windwiny.ubt@gmail.com> wrote:
>>>>
>>>> vs = (1..9).to_a
>>>> => [1, 2, 3, 4, 5, 6, 7, 8, 9]
>>>>
>>>> v1 = vs.select { |n| if n==3..n==6 then 1 end }
>>>
>>>
>>> What do you expect n==3..n==6 to do? That evaluates to a range of
>>> booleans, depending on the value of n:
>>
>>
>> These are so-called flip-flops, and a valid though obscure feature of Ruby.
>> Here's a nicer test case:
>>
>> irb(main):001:0> (1..100).each do |i|
>> irb(main):002:1*   puts i if i==42..i==45
>> irb(main):003:1> end
>> 42
>> 43
>> 44
>> 45
>>
>
> I really do not understand how this works. I can see what it produces, but why?
>
You can see a detailed explanation at
http://ruby.about.com/od/convolutedconstructions/ss/The-Curious-Case-Of-The-Flip-Flop.htm

Regards,

Park Heesob