From: Mike Leddy <mike@...>
Date: 2011-06-18T00:00:27+09:00
Subject: [ruby-core:37199] Surprised by Array#delete_if in Ruby 1.9.2

Hello,

Being familiar with the use of Array#delete and Array#delete_at which return
the item deleted I was somewhat surprised by the behaviour of Array#delete_if
returning the resultant array and NOT an array of the items that were deleted.

I would like to argue that it should return the items that are deleted:

+ Maintain similarity with Array#delete, and Array#delete_at "principle of 
  least surprise"
+ To really be the complement of Array#keep_if which "correctly" returns
  the array that is 'kept'.
+ Writing code that achieves the same effect is a little difficult to read
  and requires another variable (using parallel assignment + 
  Enumerator#partition) eg:

    b, a = a.partition {|x| x%2==0}

Anyone else agree ?

Thanks,

Mike