From: dblack@...
Date: 2007-08-08T22:49:46+09:00
Subject: Re: Iterating list in pairs

Hi --

On Wed, 8 Aug 2007, Jano Svitok wrote:

> On 8/8/07, FireAphis <FireAphis@gmail.com> wrote:
>> Hello,
>>
>> I need to iterate through a list and handle two elements on every
>> iteration. That is I'd like to do something like
>>
>> [1,2,3,4,5].each { |x, y| puts x.to_s + y.to_s }
>>
>> 12
>> 23
>> 34
>> 45
>>
>> This code doesn't work off course.
>> I can iterate using indices
>>
>> 0.upto(list.size-1) { |i| puts list[i] + list[i+1] }
>>
>> But it looks ugly to me. Do you know any elegant tricks that don't use
>> list indices?
>>
>> Thanks
>> FireAphis
>
> Enumerable#each_slice(n) {|...| ...}

That won't work because it won't double back; you'll get 12, 34, 5
instead of 12, 23, 34, 45.

However, you reminded me of something:

   require 'enumerator'
   [1,2,3,4,5].enum_cons(2).each {|a,b| puts "#{a}#{b}" }


David

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