How to iterate over an array in overlapping groups of n elements?

Question

Let's say you have this array:

arr = w|one two three|

How can I iterate over it having two consecutive elements as block arguments like this:

1st cycle: |nil, 'one'|
2nd cycle: |'one', 'two'|
3rd cycle: |'two', 'three'|

Zophar I only came with this:

arr.each_index { |i| [i - 1 < 0 ? nil: arr[i - 1], arr[i]] }

Any better solutions? Is there something like each(n)

?

+3

Alex Popov 04 dec. 14 at 8:59 am

2 answers

> [1, 2, 3, 4, 5, 6, 7, 8, 9].each_cons(2).to_a
# => [[1, 2], [2, 3], [3, 4], [4, 5], [5, 6], [6, 7], [7, 8], [8, 9]]

+3

Hetal Khunti 04 dec. At 9:05 am

Marek Lipka · Accepted Answer · 2014-12-04T09:00:43+0000

You can add nil

as the first element of yours arr

and use the method Enumerable#each_cons

:

arr.unshift(nil).each_cons(2).map { |first, second| [first, second] }
# => [[nil, "one"], ["one", "two"], ["two", "three"]]

(I am using map

here to show what exactly is returned on each iteration)