A C extension alternative to using flatten.compact or flatten.map. Slight performance improvement (just a constant factor better) than the common idioms, with exactly the same memory performance.

See this blog post for the background and a chart of memory performance.

In addition, collapse makes two other slightly different choices from core Ruby's flatten. 1. Attempting to flatten a recursive Array will error normally. collapse just drops the recursive reference, and continues on its merry way. 2. collapse doesn't accept a level argument. It's all or nothing.

Should you use this? Needing to compile a native extension for a performance benefit that is not asymptotic is a trade-off I wouldn't always make myself.

Add this line to your application's Gemfile:

gem 'array_collapse'

And then execute:

$ bundle

Or install it yourself as:

$ gem install array_collapse

2.2.2 :001 > require 'array_collapse'
 => true
2.2.2 :002 > [1, 2, [3], nil].collapse {|e| e.nil? ? e : e * 2 }
 => [2, 4, 6]
2.2.2 :003 > [1, [2, [3, nil]]].collapse
 => [1, 2, 3]
2.2.2 :004 > a = [1, [2, [3]]]
 => [1, [2, [3]]]
2.2.2 :005 > a << a
 => [1, [2, [3]], [...]]
2.2.2 :006 > a.collapse {|e| e * 3 }
 => [3, 6, 9]
2.2.2 :007 > a.flatten
 => ArgumentError: tried to flatten recursive array

Bug reports and pull requests are welcome on GitHub. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

The gem is available as open source under the terms of the MIT License.