Comments on: Iteration Shouldn’t Spin Your Wheels!

By: Evan Phoenix

Evan Phoenix — Thu, 28 Jan 2010 17:35:55 +0000

Oh geez! So sorry about the Array#map confusion. 1.8.7 is a bit inconsistent about when Enumerators are returned. You can instead do:

ary.dup.map!.with_index { |e,i| … }

Or as Ryan pointed out

ary.to_enum(:map).with_index { |e,i| … }

Sorry for the confusion.

By: Tom

Tom — Thu, 28 Jan 2010 15:57:47 +0000

Yeah, thanks for the misinformation.

By: miky

miky — Thu, 28 Jan 2010 13:18:20 +0000

Thank you for the article.

AFAIK what you've said about enumerators apply only to ruby >= 1.9

$ irb

irb(main):001:0> RUBY_VERSION

=> "1.9.2"

irb(main):002:0> ary = [1,3,5]

=> [1, 3, 5]

irb(main):003:0> ary.map

=> #

irb(main):004:0> exit

$ rvm use ruby-1.8.7

Now using ruby 1.8.7 p248

$ irb

irb(main):001:0> ary = [1,3,5]

=> [1, 3, 5]

irb(main):002:0> ary.map

=> [1, 3, 5]

irb(main):003:0> ary.map.class

=> Array

By: Gabe da Silveira

Gabe da Silveira — Thu, 28 Jan 2010 07:46:14 +0000

I was feeling pretty smug about my Ruby knowledge until the last one about Enumerators which was brand new to me. Awesome!

By: Ryan Briones

Ryan Briones — Thu, 28 Jan 2010 03:21:16 +0000

I sent this to a coworker because he thought he needed to write his own "map with index" a couple of weeks ago. On 1.8.7, at least the 1.8.7 provided by default with Snow Leopard, map always seems to return an array; not an Enumerator. *sad face*

However I did get the following to work:

[1,2,3].to_enum(:map).with_index { |f, i| [f, i] }

Thanks for the article!