From: RichardOnRails <RichardDummyMailbox58407@...>
Date: 2009-10-30T22:45:14+09:00
Subject: Re: Ruby doesn't implement x++ for Fixnum's because ???

On Oct 29, 9:18 pm, RichardOnRails
<RichardDummyMailbox58...@USComputerGurus.com> wrote:
> Hi,
>
> In The Well Grounded Rubyist (which,  along with The Ruby Way, I
> love),  Dave Black presents a justification for the x++ omission in
> Ruby.  I thought I'd see whether I could implement just the
> incrementing portion of C's x++ functionality (without the prefix/
> postfix issues) in pure Ruby.  I wasn’t willing to delve into Matz’
> implementation of higher-level Ruby functions or low-level C/C++
> code.  Below is what I came up with.
>
> Q1.  Test 1 failed, I imagine,  because the interpret thought “Ah, 7’s
> a Fixnum which I ‘ve seen billions of times, so I know what to do with
> it.”  Thus,  it ignored my over-riding definition of Fixnum.  So I
> call it “compiler error”, to use the vernacular,  by reporting that x
> had no method “pp”.  Am I all wet?
>
> Test 2 passed,  but it with a couple of anomalies:
>
> Q2. x.to_s yielded x’s class and address, suggesting x had become a
> “semi-Fixed Num”, i.e, x now stored a REFERENCE to the to x’s data,
> rather than the immediate storage of the data, as interpreter is wont
> to do with Fixnum’s.  Am I all wet?
>
> Q3. y.inspect yielded only it’s value (8) and nothing else,
> suggesting the x.pp yielded a full-fledged Fixnum.    Am I all wet?
>
> Dave Black argues that since Fixnum values use immediate storage
> rather than referenced storage, x=1;x++ would be akin to changing 1
> into 2.  This example somewhat supports that view,  but the
> interpreter sidestepped the matter by creating a reference for x’s
> value and an immediate value for y (=x.pp).
>
> Any ideas,
> Richard
>
> class FixNum
>   attr :val
>   def initialize (fixnum)
>     puts "Initializing object %d" % fixnum
>     raise "Initializer not a Fixnum" if
>         fixnum.class != Fixnum
>     puts "\nInitializing Fixnum to %d" % fixnum
>     @val = fixnum
>   end
>
>   def pp
>     @val+=1
>   end
> end
>
> # Test 1 (Failure)
> x = 7;  y = x.pp; z =x.class # undefined method `pp' for 7:Fixnum
> (NoMethodError)
>
> # Test 2 (Success)
> x = FixNum.new(7);  y = x.pp; z =x.class
> puts [x.to_s, y.inspect, z.to_s].join("; ") # => <FixNum:0x2b62694>;
> 8; FixNum

Hi,

Please ignore my questions.  I just discovered a major mistake: I
thought I was overriding Ruby's Fixnum class,  but I misspelled it at
FixNum.  That error invalidates most if not all of the things I
reported.  Mea Culpa.

I'll correct my errors and probably have a new theory subsequently.

Best wishes,
Richard