From: Justin Collins <justincollins@...>
Date: 2009-10-03T03:35:21+09:00
Subject: Re: Rolling String Buffer needed

Matt Brooks wrote:
> Aaron Patterson wrote:
>   
>> class MyBuff
>>    def initialize max_size, filename
>>      @max_size = max_size
>>      @list = []
>>      @file = File.open(filename, 'wb')
>>    end
>>
>>    def push string
>>      @list.push string
>>      while @list.length > @max_size
>>        @file.write @list.pop
>>      end
>>    end
>>
>>    def [] i
>>      @list[i]
>>    end
>> end
>>
>> ---
>> Aaron Patterson
>> http://tenderlovemaking.com
>>     
>
>
> That looks great!  So when I do pop on an array it does the highest 
> index element?  And when you push onto an array it puts it in index 0 ?
>
> Thanks!
> Matt
>
>   

Actually, push/pop works like it's a stack, with the top being the last 
element. So pop removes and returns the last element, while push appends 
to the end.

irb(main):001:0> a = [1,2,3,4]
=> [1, 2, 3, 4]
irb(main):002:0> a.pop
=> 4
irb(main):003:0> a.push 5
=> [1, 2, 3, 5]
irb(main):004:0> a.pop
=> 5
irb(main):005:0> a
=> [1, 2, 3]

If you want it to act like a queue with the first element being the 
head, then use shift/push.

rb(main):001:0> a = [1,2,3,4]
=> [1, 2, 3, 4]
irb(main):002:0> a.shift
=> 1
irb(main):003:0> a.push 5
=> [2, 3, 4, 5]
irb(main):004:0> a.shift
=> 2
irb(main):005:0> a
=> [3, 4, 5]

If you want it to act like a queue with the last element being the head, 
then use pop/unshift.

irb(main):001:0> a = [1,2,3,4]
=> [1, 2, 3, 4]
irb(main):002:0> a.pop
=> 4
irb(main):003:0> a.unshift 5
=> [5, 1, 2, 3]
irb(main):004:0> a.pop
=> 3
irb(main):005:0> a
=> [5, 1, 2]


-Justin