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Groups > comp.lang.java.programmer > #22632
| From | Arved Sandstrom <asandstrom2@eastlink.ca> |
|---|---|
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: BlueJ don't know what i did wrong |
| References | (16 earlier) <672dncokKZ13AbHMnZ2dnUVZ8oadnZ2d@bt.com> <DtlXs.167113$EO2.133976@newsfe04.iad> <PYednV_FAPpyZ7DMnZ2dnUVZ7oKdnZ2d@bt.com> <lszXs.40705$BV7.24274@newsfe24.iad> <FKKdnfAtKZlrh7LMnZ2dnUVZ7oidnZ2d@bt.com> |
| Message-ID | <IMPXs.145744$j95.20544@newsfe31.iad> (permalink) |
| Organization | Public Usenet Newsgroup Access |
| Date | 2013-02-28 17:14 -0400 |
On 02/28/2013 04:53 AM, lipska the kat wrote: > On 28/02/13 02:40, Arved Sandstrom wrote: >> On 02/27/2013 08:24 AM, lipska the kat wrote: >>> On 27/02/13 10:45, Arved Sandstrom wrote: >>>> On 02/26/2013 07:30 AM, lipska the kat wrote: >>>>> On 26/02/13 09:59, Arved Sandstrom wrote: >>>>>> On 02/26/2013 05:23 AM, lipska the kat wrote: > > [snip] > >> I'm happy with the definition that for example Knuth or Sedgwick use >> (and about a million other people), where a deque is called a >> generalization of a queue or a stack. The reason a deque is called a >> generalization of a queue or a stack is because it is in fact more >> general than a queue or a stack, and combines features of both. >> >> Since a whole raft of CS authorities and other programming commentators >> are happy to call the deque a generalization of a queue or stack when >> writing about data structures, I'm pretty happy to accept this as a >> definition. > > Yep, I agree, my stubborn determination to prove you wrong about this > issue clouded my judgment. On this I concede. I am human, I am > imperfect, I make mistakes. > > However > > I simply cannot agree with your assertion that > > "a deque is not a queue, but a queue is a deque." > > Enter the following into your favorite IDE > > java.util.Queue queue = null; > java.util.Deque deque = null; > > queue = deque; > //This compiles: Because we can store a reference to a Deque into a > //reference to a Queue, a Deque *is a* Queue > > deque = queue; > //This does not compile: Because we can't store a reference > //to a Queue into a reference to a Deque, a Queue *is not* a Deque > > If a Queue were a Deque then we could call Deque methods on a Queue > Can we call Deque methods on a Queue? well I can't, can you? > > I'd be interested to hear your thoughts on this. > > lipska I'm not sure I agree with one of my original statements either, now that I really think things through. We're talking several different notions of "generalization". These conflict pretty badly. Sticking with generalization as in generalization & specialization, and supertypes and subtypes, on second thought I'd have to agree with you. A deque is a generalization of queue and stack in the sense that it is more general; it has the operations to support use as either a queue or a stack. It's multiple inheritance (conceptually if not for real) that gives us this mix. This was an interesting discussion. I now want to go and pound nails into my forehead. Just goes to show that a body needs to be really careful about CS statements like "a deque is a generalization of queue and stack", because in UML/OO terms it's actually not. AHS
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BlueJ don't know what i did wrong BlueJguywithoutskill <marvin.radke@htp-tel.de> - 2013-02-22 06:03 -0800
Re: BlueJ don't know what i did wrong Joerg Meier <joergmmeier@arcor.de> - 2013-02-22 15:55 +0100
Re: BlueJ don't know what i did wrong marvin.radke@htp-tel.de - 2013-02-22 07:13 -0800
Re: BlueJ don't know what i did wrong Joerg Meier <joergmmeier@arcor.de> - 2013-02-22 16:24 +0100
Re: BlueJ don't know what i did wrong marvin.radke@htp-tel.de - 2013-02-22 07:31 -0800
Re: BlueJ don't know what i did wrong Eric Sosman <esosman@comcast-dot-net.invalid> - 2013-02-22 10:50 -0500
Re: BlueJ don't know what i did wrong markspace <markspace@nospam.nospam> - 2013-02-22 10:43 -0800
Re: BlueJ don't know what i did wrong marvin.radke@htp-tel.de - 2013-02-24 02:27 -0800
Re: BlueJ don't know what i did wrong Joerg Meier <joergmmeier@arcor.de> - 2013-02-24 14:54 +0100
Re: BlueJ don't know what i did wrong marvin.radke@htp-tel.de - 2013-02-24 06:15 -0800
Re: BlueJ don't know what i did wrong lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-24 15:04 +0000
Re: BlueJ don't know what i did wrong lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-24 16:29 +0000
Re: BlueJ don't know what i did wrong Joerg Meier <joergmmeier@arcor.de> - 2013-02-24 18:21 +0100
Re: BlueJ don't know what i did wrong lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-24 17:43 +0000
Re: BlueJ don't know what i did wrong Joerg Meier <joergmmeier@arcor.de> - 2013-02-24 20:04 +0100
Re: BlueJ don't know what i did wrong lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-24 19:24 +0000
Re: BlueJ don't know what i did wrong marvin.radke@htp-tel.de - 2013-02-25 01:52 -0800
Re: BlueJ don't know what i did wrong lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-25 11:10 +0000
Re: BlueJ don't know what i did wrong "John B. Matthews" <nospam@nospam.invalid> - 2013-02-25 07:50 -0500
Re: BlueJ don't know what i did wrong lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-25 13:35 +0000
Re: BlueJ don't know what i did wrong "John B. Matthews" <nospam@nospam.invalid> - 2013-02-25 13:52 -0500
Re: BlueJ don't know what i did wrong lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-25 19:54 +0000
Re: BlueJ don't know what i did wrong Lew <lewbloch@gmail.com> - 2013-02-25 14:26 -0800
Re: BlueJ don't know what i did wrong lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-26 09:08 +0000
Re: BlueJ don't know what i did wrong Arne Vajhøj <arne@vajhoej.dk> - 2013-02-25 22:05 -0500
Re: BlueJ don't know what i did wrong Arne Vajhøj <arne@vajhoej.dk> - 2013-02-25 22:08 -0500
Re: BlueJ don't know what i did wrong lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-26 09:23 +0000
Re: BlueJ don't know what i did wrong Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-02-26 05:59 -0400
Re: BlueJ don't know what i did wrong lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-26 11:30 +0000
Re: BlueJ don't know what i did wrong Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-02-27 06:45 -0400
Re: BlueJ don't know what i did wrong lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-27 11:58 +0000
Re: BlueJ don't know what i did wrong lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-27 12:24 +0000
Re: BlueJ don't know what i did wrong Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-02-27 22:40 -0400
Re: BlueJ don't know what i did wrong lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-28 08:53 +0000
Re: BlueJ don't know what i did wrong Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-02-28 17:14 -0400
Re: BlueJ don't know what i did wrong lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-03-01 08:45 +0000
Re: BlueJ don't know what i did wrong markspace <markspace@nospam.nospam> - 2013-02-26 08:33 -0800
Re: BlueJ don't know what i did wrong Arne Vajhøj <arne@vajhoej.dk> - 2013-02-25 22:19 -0500
Re: BlueJ don't know what i did wrong Arne Vajhøj <arne@vajhoej.dk> - 2013-02-25 22:02 -0500
Re: BlueJ don't know what i did wrong marvin.radke@htp-tel.de - 2013-02-25 09:54 -0800
Re: BlueJ don't know what i did wrong lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-25 18:25 +0000
Re: BlueJ don't know what i did wrong Joerg Meier <joergmmeier@arcor.de> - 2013-02-26 16:13 +0100
Re: BlueJ don't know what i did wrong lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-02-26 16:40 +0000
Re: BlueJ don't know what i did wrong Joerg Meier <joergmmeier@arcor.de> - 2013-02-26 18:19 +0100
Re: BlueJ don't know what i did wrong markspace <markspace@nospam.nospam> - 2013-02-25 08:34 -0800
Re: BlueJ don't know what i did wrong Lew <lewbloch@gmail.com> - 2013-02-24 12:38 -0800
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