From: SonOfLilit <sonoflilit@...>
Date: 2007-02-20T06:56:12+09:00
Subject: Re: The peak of the iceberg, was Range cannot loop down and RCR Integer#pred

Well, perhaps we both didn't understand each other :-)

I'll try to be clearer and also understand your points better.

On 2/19/07, Robert Dober <robert.dober@gmail.com> wrote:
> On 2/19/07, SonOfLilit <sonoflilit@gmail.com> wrote:
> > -1
>
> First I want to say that I do not mind hijacking threads at all so be
> me guest ;)
> But I have not talked about the things you are talking here.
> >
> > Though I can understand why it looks like an iceberg, I think it's one
> > of those programmer icebergs that we invent to complete sets.
> The iceberg is somewhere else but I do not want to talk about it yet.
> >
> > Why?
> >
> > #succ is for #each .
> >
> > #each is truly essential, as it gives totally new functonality.
> >
> > #pred would be for a "different order of each".
> No sir, your interpretation, I do not advocate a different order of
> each I am only talking about #pred.
>

Have you found useful uses of #pred in a general case (not just for
Integer) that is not essentially built on iteration? If so, I
apologize. I couldn't find any clue to the existence of such from your
post. Would you please elaborate?

> It was just when I wanted for demonstration purpose implement a
> generic reverse_each that I realized that I was missing #pred in a
> more general way.
>

What is this more general way?

> > Now, yes, I do know
> > that there /is/ some use for reverse-each, but there are MANY OTHER
> > different order-eaches that are as important. That's why
> > #to_a.reverse.each is for those cases, that aren't so abundant as to
> > /need/ a #reverse_each .
> >
> > If a fast reverse_each is needed, it's usually about numbers and then
> > you have Numeric#step .
> >
> >
> > Perhaps there would be use for this as a library, MAYBE even a
> > standard library, but I wouldn't throw this in core Ruby.
> What I am talking about *is* already in the core for Integer and I am
> drying to apply the same logic to other #succ receivers.
>
> I really feel very bad not having given enough thought to the RCR.
> >
> > reverse_each isn't more useful than any other case of sorted_each.
> That could be argued but is completely OT.

What I meant is that any use case of #pred I could find is a use case
that I would attribute to "traverse the range in an arbitrary order".
Not because it is more general, just because it fits the thought
template of it. It "feels" like a particular case of aforementioned
abstraction, and not like a particular abstraction.

> >
> > Hmm, maybe we should implement that (no ue really, it's so slow it's
> > better left out of the path of least resistance.)
> >
> >
> Again you'r making valid and reasonable points, no problem with that,
> but they are not related to what I wanted to say. Well I feel at
> least.
>

What use cases for #pred did you find that you were missing?

> Robert
> --
> We have not succeeded in answering all of our questions.
> In fact, in some ways, we are more confused than ever.
> But we feel we are confused on a higher level and about more important things.
> -Anonymous
>
>