From: Robert Klemme <shortcutter@...>
Date: 2007-12-08T20:00:00+09:00
Subject: Re: for loop iterator, next object

On 04.12.2007 23:18, Christian von Kleist wrote:
> On Dec 4, 2007 4:55 PM, lpgauth@gmail.com <lpgauth@gmail.com> wrote:
>> On Dec 4, 4:19 pm, MenTaLguY <men...@rydia.net> wrote:
>>> On Wed, 5 Dec 2007 05:42:21 +0900, MenTaLguY <men...@rydia.net> wrote:
>>>> On Wed, 5 Dec 2007 05:35:01 +0900, "lpga...@gmail.com" <lpga...@gmail.com>
>>>> wrote:
>>>>> Assume I have:
>>>>>    for user in @Users
>>>>>       put user.name
>>>>>       put user.name #I want this to be next object in @Users
>>>>>    end
>>>>> I want the second user.name to be the next object in the list. Is
>>>>> there a way to do this?
>>>> Of course.  But what do you want to happen when you're at the end
>>>> of the list and there is no longer a next object?
>>> That is, if you only care about pairs of users, then you can do this:
>>>
>>>  prior = nil
>>>  for user in @Users
>>>    if prior
>>>      put prior.name
>>>      put user.name
>>>    end
>>>    prior = user
>>>  end
>>>
>>> Obviously that won't print anything if there is only one entry in
>>> @Users, though.
>>>
>>> -mental
>> I figured it out... You can use in_group_of
>>
>>
> 
> 
> Cool!  That's from Rails (not part of Ruby), but there's also each_slice(n):
> 
> require 'enumerable'
> 
> a = [1, 2, 3, 4]
> 
> a.each_slice(2) {|slice| puts slice[0] + slice[1]}

I'd probably rather use #each_cons:

irb(main):001:0> %w{a b c}.each_cons(2) {|*a| p a}
[["a", "b"]]
[["b", "c"]]
=> nil

Cheers

	robert