From: Michael Fellinger <m.fellinger@...>
Date: 2008-09-26T04:23:07+09:00
Subject: Re: Getting the right class with inheritance and super()

On Fri, Sep 26, 2008 at 12:41 AM, Kyle Schmitt <kyleaschmitt@gmail.com> wrote:
> On Thu, Sep 25, 2008 at 9:51 AM, Robert Klemme
> <shortcutter@googlemail.com> wrote:
>> Since I would recommend using delegation instead of inheritance you
>> don't have to.  If you use inheritance you must make sure that your
>> class's invariant is not broken.
>
> Upon thinking about it more, and attempting to flush it out in the
> inheritence direction, I'm coming to agreement about encapsulate
> instead.
>
>>> I'd like it to.  This was a first blush since I needed (more wanted,
>>> but anyway) it in this project.
>>
>> If you think about it for a moment you'll realize that your
>> FixesSizedArray is far from usable in every place where an Array is
>> used.  Just think about algorithms that rely on collecting arbitrary
>> many objects in an Array (e.g. File.readlines) - you cannot use your
>> FixedSizedArray there.
>
> I agree that it can't be used everywhere, but where I want to use it,
> I want it to look and feel very much like an array.
> However, the case of File.readlines may be an example of exactly how
> I'd like to use it:  it gives you a fixed amount of data.
> f=FixedSizeArray.new(100)
> f<<File.readlines("/var/log/messages")

This should be:
f = FixedSizeArray.new(100)
f.concat File.readlines("/var/log/messages").first(100)

First of all you won't end up with an Array with n elements as first
element in your FixedSizeArray, and it also tells the reader which of
the lines will be used (you may want to use #last instead, depending
on your implementation).
I think it would be nice to have a behaviour as if you would #each
over the incoming array and push each element on the fixed size array,
but YMMV.

^ manveru

> Then the question becomes does the principle of least surprise.  Is it
> least surprising to read in the first 100 lines, in this case, and
> ignore the rest, or is it least surprising to let the 100 line window
> slide to the end, and only deal with the last hundred?
>
> --Kyle