From: David Alan Black <dblack@...>
Date: 2004-05-08T21:54:02+09:00
Subject: Re: How to get the last 5 elements of an array?

Hi --

Gavin Sinclair <gsinclair@soyabean.com.au> writes:

> On Saturday, May 8, 2004, 10:24:02 PM, Xavier wrote:
> 
> > But [1,2][-5,5] =>> nil
> > and Gavin wants [1,2] instead of nil
> 
> > How about
> 
> > def last5(arr)
> >  if arr.length<5 then arr else arr[-5,5] end
> > end
> 
> 
> Right.  Now should that be necessary?  Grabbing the last 5 elements of
> an array is the kind of thing that should be easy and obvious in Ruby.
> 
> So I propose that Array be changed so that
> 
>   def last5(arr)
>     arr[-5..-1]
>   end
> 
> meets the requirements I gave earlier.  That is
> 
>   last5 []                  # -> []
>   last5 [1]                 # -> [1]
>   last5 [1,2]               # -> [1,2]
>   last5 [1,2,3,4,5,6,7]     # -> [3,4,5,6,7]
>   last5 nil                 # -> error
> 
> 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.

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

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


David

-- 
David A. Black
dblack@wobblini.net