From: Xavier <NOSPAM@...>
Date: 2004-05-08T21:24:02+09:00
Subject: Re: How to get the last 5 elements of an array?

On Sat, 08 May 2004 21:14:05 +0900, Martin Stannard wrote:

> On Sat, 2004-05-08 at 22:08, Gavin Sinclair wrote:
>> Hi,
>> 
>> I want to extract the last 5 elements of an array 'x'.  I know that x
>> is an array, but I don't know how many elements it has.  What do you
>> suggest?
>> 
>> In code, this is what I want.
>> 
>>   def last5(arr)
>>     # Fill me in.
>>   end
>> 
>>   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
>> 
>> Thanks,
>> Gavin
>> 
> 
> Hi Gavin,
> 
> ruby -e 'p [1, 2, 3, 4, 5, 6, 7, 8, 9, 10][-5..-1]'
> 
> Martin

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
last5 []
=> []
last5 [1]
=> [1]
last5 [1,2]
=> [1, 2]
last5 [1,2,3,4,5,6,7]
=> [3, 4, 5, 6, 7]
last5 nil
NoMethodError: undefined method `length' for nil:NilClass
        from (irb):12:in `last5'
        from (irb):18