Misha Moroshko Misha Moroshko - 2 years ago 260
Ruby Question

How to map with index in Ruby?

What is the easiest way to convert

[x1, x2, x3, ... , xN]


[[x1, 2], [x2, 3], [x3, 4], ... , [xN, N+1]]

Answer Source

If you're using ruby 1.8.7 or 1.9, you can use the fact that iterator methods like each_with_index, when called without a block, return an Enumerator object, which you can call Enumerable methods like map on. So you can do:

arr.each_with_index.map { |x,i| [x, i+2] }

In 1.8.6 you can do:

require 'enumerator'
arr.enum_for(:each_with_index).map { |x,i| [x, i+2] }
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