From: Gavin Sinclair <gsinclair@...>
Date: 2004-05-08T22:24:14+09:00
Subject: Re: How to get the last 5 elements of an array?

On Saturday, May 8, 2004, 10:54:02 PM, David wrote:

>> Any thoughts before I raise an RCR?
> 
> Yes.  I don't think it makes sense for this:
> 
>   arr[-5..-1].include?(arr[-3])
> 
> to be false, since this:
> 
>   (-5..-1).include?(-3)
> 
> is true.

Your first condition would be justifiably false if arr == [1,2], even
if I submitted an RCR and it were accepted and implemented.

> But none of this matters, because Array#last takes an argument :-)

>   irb(main):008:0> [1,2,3].last(2)
>   => [2, 3]

Sweet!  Learn something new every day.  That quells the desire for an
RCR, because I'm not sure of the theoretical ground for such, your
example notwithstanding.

For example, consider this:

  x = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
  x[-5..3]  # -> nil

If even *that* returns nil, when *all* numbers in the range are valid
indexes, then...

Also, there's everybody's favourite example:

  x[10..15] # -> []
  x[11..15] # -> nil

I'd rather see 'arr[range]' *always* return an array, no matter the
value of 'arr' and 'range'.

Thanks,
Gavin