Ruby Programming Language :: #<Object:0x2c1c8f0> <--- why is the displayed number == object


	#<Object:0x2c1c8f0> <--- why is the displayed number == object_id*2 irb(main):001:0> VERSION => "1.8.5" irb(main):002:0> o=Object.new => #<Object:0x2c1c8f0> irb(main):003:0> ObjectSpace._id2ref 0x2c1c8f0 RangeError: 0x2c1c8f0 is not id value from (irb):3:in `_id2ref' from (irb):3 irb(main):004:0> ObjectSpace._id2ref 0x2c1c8f0/2 => #<Object:0x2c1c8f0> irb(main):005:0> I think that is pretty confusing. I am sure there is a good reason for this. But, don't you think it'd be better to display the real object_id instead of the doubled value? -- henon In message <43d756720706060810s53f67ec8yc9c0f3734d1f2@mail.gmail.com>, "Meinrad Recheis" wri tes: >irb(main):001:0> VERSION >=> "1.8.5" >irb(main):002:0> o=Object.new >=> #<Object:0x2c1c8f0> >irb(main):003:0> ObjectSpace._id2ref 0x2c1c8f0 >RangeError: 0x2c1c8f0 is not id value > from (irb):3:in `_id2ref' > from (irb):3 >irb(main):004:0> ObjectSpace._id2ref 0x2c1c8f0/2 >=> #<Object:0x2c1c8f0> >irb(main):005:0> >I think that is pretty confusing. I am sure there is a good reason for >this. But, don't you think it'd be better to display the real >object_id instead of the doubled value? Maybe it would. That said, Object.object_id works as expected, so this only affects irb's display. (The reason, presumably, is that the ID is left-shifted by one, because objects with a 1 in the low-order bit are fixnums.) -s On 06.06.2007 17:10, Meinrad Recheis wrote: > irb(main):001:0> VERSION > => "1.8.5" > irb(main):002:0> o=Object.new > => #<Object:0x2c1c8f0> > irb(main):003:0> ObjectSpace._id2ref 0x2c1c8f0 > RangeError: 0x2c1c8f0 is not id value > from (irb):3:in `_id2ref' > from (irb):3 > irb(main):004:0> ObjectSpace._id2ref 0x2c1c8f0/2 > => #<Object:0x2c1c8f0> > irb(main):005:0> > I think that is pretty confusing. I am sure there is a good reason for > this. But, don't you think it'd be better to display the real > object_id instead of the doubled value? The output of #inspect is not meant to give you any means to get at the original object although it may seem so at times. Having said that, #object_id and #inspect are completely unrelated and it's just an implementation artifact that some classes actually return something that resembles the object id. As far as I remember this list you are the first one that mentions this. So it's probably not that big an issue (at least not as confusing as "singleton class" :-)) Kind regards robert On 6/6/07, Robert Klemme <shortcut@googlemail.com> wrote: - Hide quoted text - > On 06.06.2007 17:10, Meinrad Recheis wrote: > > irb(main):001:0> VERSION > > => "1.8.5" > > irb(main):002:0> o=Object.new > > => #<Object:0x2c1c8f0> > > irb(main):003:0> ObjectSpace._id2ref 0x2c1c8f0 > > RangeError: 0x2c1c8f0 is not id value > > from (irb):3:in `_id2ref' > > from (irb):3 > > irb(main):004:0> ObjectSpace._id2ref 0x2c1c8f0/2 > > => #<Object:0x2c1c8f0> > > irb(main):005:0> > > I think that is pretty confusing. I am sure there is a good reason for > > this. But, don't you think it'd be better to display the real > > object_id instead of the doubled value? > The output of #inspect is not meant to give you any means to get at the > original object although it may seem so at times. Having said that, > #object_id and #inspect are completely unrelated and it's just an > implementation artifact that some classes actually return something that > resembles the object id. > As far as I remember this list you are the first one that mentions this. > So it's probably not that big an issue (at least not as confusing as > "singleton class" :-)) > Kind regards > robert Robert, Thanks for your answer. I came across it while debugging a running application via an eval console. It's not really a problem because I know that I need to divide the displayed id by 2 to get the object. I posted it just because ruby didn't work as I expected it to ... which is completely against the principles of the language. cheers, -- henon On 07.06.2007 17:39, Meinrad Recheis wrote: - Hide quoted text - > On 6/6/07, Robert Klemme <shortcut@googlemail.com> wrote: >> On 06.06.2007 17:10, Meinrad Recheis wrote: >> > irb(main):001:0> VERSION >> > => "1.8.5" >> > irb(main):002:0> o=Object.new >> > => #<Object:0x2c1c8f0> >> > irb(main):003:0> ObjectSpace._id2ref 0x2c1c8f0 >> > RangeError: 0x2c1c8f0 is not id value >> > from (irb):3:in `_id2ref' >> > from (irb):3 >> > irb(main):004:0> ObjectSpace._id2ref 0x2c1c8f0/2 >> > => #<Object:0x2c1c8f0> >> > irb(main):005:0> >> > I think that is pretty confusing. I am sure there is a good reason for >> > this. But, don't you think it'd be better to display the real >> > object_id instead of the doubled value? >> The output of #inspect is not meant to give you any means to get at the >> original object although it may seem so at times. Having said that, >> #object_id and #inspect are completely unrelated and it's just an >> implementation artifact that some classes actually return something that >> resembles the object id. >> As far as I remember this list you are the first one that mentions this. >> So it's probably not that big an issue (at least not as confusing as >> "singleton class" :-)) > Thanks for your answer. I came across it while debugging a running > application via an eval console. It's not really a problem because I > know that I need to divide the displayed id by 2 to get the object. Well, but that won't work for all cases. > I > posted it just because ruby didn't work as I expected it to ... which > is completely against the principles of the language. That's only one way to look at it. The other way is of course to assume that your expectations were "wrong" (whatever that means). :-) Kind regards robert On 6/7/07, Robert Klemme <shortcut@googlemail.com> wrote: > On 07.06.2007 17:39, Meinrad Recheis wrote: > > On 6/6/07, Robert Klemme <shortcut@googlemail.com> wrote: > >> As far as I remember this list you are the first one that mentions this. > >> So it's probably not that big an issue (at least not as confusing as > >> "singleton class" :-)) > > Thanks for your answer. I came across it while debugging a running > > application via an eval console. It's not really a problem because I > > know that I need to divide the displayed id by 2 to get the object. > Well, but that won't work for all cases. Nor for all versions of ruby. The relationship between object_id and the VALUE representation for various classes has been changing even within the 1.8.x stream. $Diety only knows what implementations like JRuby, rubinius, IronRuby etc would use for inspect which is the method which produces what you see after the ==> in irb, or call Kernel#p Inspect is intended to be used for the 'programmer' representation of an object, to help activities like debugging. So in the case of classes like Object that representation will likely have some info useful to the current internal implementation, and unless it's documented somewhare, there's no guarantee that it won't change. -- Rick DeNatale My blog on Ruby http://talklikeaduck.denhaven2.com/ On Jun 6, 8:21 am, s@seebs.net (Peter Seebach) wrote: > (The reason, presumably, is that the ID is left-shifted by one, because > objects with a 1 in the low-order bit are fixnums.) When I came across this behavior, this was also my best guess as the reason.

Ruby Programming Language

#<Object:0x2c1c8f0> <--- why is the displayed number == object_id*2