From: Robert Klemme <shortcutter@...>
Date: 2010-05-31T17:34:46+09:00
Subject: Re: enumerator problem in 1.9.1

2010/5/31 botp <botpena@gmail.com>:
> On Mon, May 31, 2010 at 9:04 AM, Bug Free <amberarrow@yahoo.com> wrote:
>> The following line:
>>
>>    [5, 7].each_with_index.each_cons(2) {|v| p v }
>>
>> prints [5, 7] but I'm expecting [[5, 0], [7, 1]].
>
> you'll have specify the index, eg,
>
>>>  [5, 7].map.with_index{|v,i| [v,i]}
> => [[5, 0], [7, 1]]

That's not the proper replacement with map.  Rather you'd do:

irb(main):009:0> [5, 7].each_with_index.map {|v| v }
=> [5, 7]
irb(main):010:0> [5, 7].each_with_index.map {|*v| v }
=> [[5, 0], [7, 1]]

Interestingly the splat operator does not include the index with #each_cons:

irb(main):011:0> [5, 7].each_with_index.each_cons(2) {|v| p v }
[5, 7]
=> nil
irb(main):012:0> [5, 7].each_with_index.each_cons(2) {|*v| p v }
[[5, 7]]
=> nil

This is on ruby 1.9.1p378 (2010-01-10 revision 26273) [i386-cygwin].

I'd say it's a bug which seems to be reflected by the fact that it
works as expected in 1.9.3 according to Caleb.

Cheers

robert

-- 
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