From: Rodrigo Rosenfeld Rosas <rr.rosas@...>
Date: 2011-06-30T11:09:53+09:00
Subject: [ruby-core:37679] [Ruby 1.9 - Feature #4541] Inconsistent Array.slice()


Issue #4541 has been updated by Rodrigo Rosenfeld Rosas.


What I think is less confusing is to always return an array when passing ranges, like the following example:

<pre>
[][1..2] #=> [] instead of nil
</pre>

Think in some practical method like this one:

<pre>
def some_method(*elements) # suppose elements can be [], maybe elements are read from some file...
  special_element = args[0] # suppose we don't want elements.shift because we will send elements to another method...
  do_something_special if special_element
  elements[1..-1].each{|el| ...} # this will raise an exception if elements == []
  call_another_method(elements)
end
</pre>

Yes, I know this is not a great example, but I'm too tired right now to think in a better one...
----------------------------------------
Feature #4541: Inconsistent Array.slice()
http://redmine.ruby-lang.org/issues/4541

Author: Marcin Pietraszek
Status: Assigned
Priority: Normal
Assignee: Yukihiro Matsumoto
Category: core
Target version: 1.9.x


=begin
Array slice/[] method is a bit inconsistent. Is it just poorly documented "feature" or a bug? In API doc I can't find this behaviour mentioned as a "special case".

 def test_array_slice
    array = ['a', 'b', 'c']
    assert_equal nil, array[3]
    assert_eaual nil, array[4]
 
    assert_eaual [], array[3, 0] #
    assert_equal nil, array[4, 0] # [] expected (or both nils in array[3, 0] and array[4, 0])
 
    assert_equal ['c'], array[2..2]
    assert_equal [], array[3..3] #
    assert_equal nil, array[4..4] # [] expected (or both nils in array[3..3] and array[4..4])
 end

Same behaviour can be reproduced on ruby 1.8.7 (2010-12-23 patchlevel 330) [x86_64-linux].
=end



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