From: "David A. Black" <dblack@...>
Date: 2009-11-11T21:51:43+09:00
Subject: Re: Ruby doesn't implement x++ for Fixnum's because ???

Hi --

On Thu, 5 Nov 2009, RichardOnRails wrote:

> Hi David,
>
> First,  Thank you for The Well-Grounded Rubyist. I study like other
> pour over scriptures or the Koran.  Your topics are well chose,
> beautifully explicated.  And Manning adding typesetting that enhanced
> the your work.

Thanks!

> I started this thread because some of your comments on page 54, e.g.
> "The un-reference ..." were a blemish among your excellent analyses.

Oh dear -- the whole thread is my fault? :-)

> The fact that Robert Klemme, whom I also respect highly as a Rubyist,
> agrees with you gives me pause.
>
> But nevertheless,  I maintain that my corrected post of today refutes
> such claims as "... any object that's represented as an immediate
> value is always the same object."

I'm afraid I don't see the refutation, but as per my previous post,
the immediate value thing is only part of the picture.

> Russel & Whitehead dealt with this
> kind of issue perhaps a century ago when the defined the first Natural
> Number, 1, as "the set of all sets that are in one-to-one
> correspondence with the set containing the Null Set." Plato dealt with
> this in The Parable of the Caves" with the claim that allegedly
> concrete things were merely reflections of the "real" objects.

Well... any given system of symbolic representation may or may not
take a Platonic view of things. Plato's allegory is of course of great
importance in the history of thought, but it doesn't really dictate
that 2000+ years later, there can't be a computer language with
identifiers housing immediate values :-)

> I'm not clamoring for a Ruby implementation.  I only posted my
> analysis on this issue to get other people's opinions.  And I find it
> hard compose a mistake free exposition, e.g. the last code lines in
> yesterday evening's post:
>
> a = 2**30-1; show (a) => Got 1073741823;  class = Fixnum;   object_id
> = 2147483647;  v >> 1 = 1073741823
> a = 2**30; show (a) => Got 1073741824;  class = Bignum;   object_id =
> 22737670;  v >> 1 = 11368835
>
> should have read:
>
> a = 2**30-1; show (a) => Got 1073741823;  class = Fixnum;   object_id
> = 2147483647;  v >> 1 = 1073741823
> show(a.pp)  =>  Got 1073741824;  class = Bignum;   object_id =
> 22738520;  v >> 1 = 11369260       # Of course, "v >> 1" is irrelevant
> here
>
> to make the point that "pp" crossed the Fixnum/Bignum boundary
> smoothly.

You'll see a lot of people cutting-and-pasting entire shell sessions,
like this:

$ cat myfile.rb
... code here ...

$ ruby myfile.rb
... output here ...

which is a good way to ensure that your output is from your input. I
rely a lot (depending on the example) on pasting things in and out of
irb.

> Bottom line:  Please keep up you great work!  I appreciate it very
> much!

I'll do me best :-)


David

-- 
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