Ruby Array.diff(other) difference between 2 Arrays

Diff is defined on Set, but not on Array, so we patch it in… (thanks to reto)
Usage
[1,2] ^ [2,3,4] == [1,3,4]

Code

class Array
  def ^(other)
    result = dup
    other.each{|e| result.include?(e) ? result.delete(e) : result.push(e) }
    result
  end unless method_defined?(:^)
  alias diff ^ unless method_defined?(:diff)
end

puts ([] ^ [1]).inspect          # [1]
puts ([1] ^ []).inspect          # [1]
puts ([1] ^ [2]).inspect         # [1,2]
puts ([] ^ []).inspect           # []
puts ([1,1] ^ [1,1,2,2]).inspect # [1]

The same could be done with (self | other) – (self & other) but would be less performant.

5 thoughts on “Ruby Array.diff(other) difference between 2 Arrays”

reto says:

2011-07-07 at 13:52:15

See also Set#^ which does the same.

Cheers,
reto

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- pragmatig says:
  
  2011-07-07 at 15:06:28
  
  Thanks for the tip, just updated the post 🙂
  
  Reply
Viktar Basharymau says:

2011-07-08 at 14:08:48

And `require ‘set’` is necessary. If the require statement is missing, `[1,2] ^ [2,3,4]` raises NameError: uninitialized constant Array::Set.

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pragmatig says:

2011-07-08 at 14:17:49

Thanks, fixed!

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pragmatig says:

2011-07-10 at 6:47:30

I rewrote it with the internal implementation from set, so this should be as performant as it gets 🙂

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