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Groups > comp.lang.c++ > #3483
| From | "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> |
|---|---|
| Newsgroups | comp.lang.c++ |
| Subject | Re: On generally accepted terminology for pointers and arrays |
| Date | 2011-04-12 16:25 +0200 |
| Organization | A noiseless patient Spider |
| Message-ID | <io1nc7$3j1$1@dont-email.me> (permalink) |
| References | <io0bnr$dph$1@dont-email.me> <NvUop.27147$rF.26993@newsfe12.ams2> |
* cpp4ever, on 12.04.2011 10:59: > On 12/04/11 03:00, Alf P. Steinbach /Usenet wrote: >> Since my killfile works I only see one side of the numerous debates here >> about pointers and arrays. >> >> But it does seem to be pretty confrontational. >> >> So, herewith, me on the subject of how to talk about pointers& arrays. >> >> When I wrote my (peer reviewed) pointers tutorial I discovered that even >> the acknowledged international experts did not agree on the meaning of >> "pointer". Happily the disagreements were mainly of the single kind >> exemplified by >> >> Hey, you can't call THAT a pointer (because I don't)! >> >> Some objected to calling variables pointers, others objected to calling >> pointer values pointers, and yet others objected to calling pointer >> types pointers, even though the Holy Standard does. In case the latter >> is difficult to grok: I'm talking about utterances like "it's a pointer" >> and "it's a car", instead of spelling it out more literally like "it's a >> something of pointer type" and "it's an object that conforms to the >> requirements of the 'car' type of vehicle". I never understood the point >> of making such subtle distinctions, but apparently some who are smarter >> and/or more knowledgable than me, do. And what about smart pointers? If >> they are accepted as pointers, then a pointer needs not necessarily be a >> pointer of the kind that the language supports directly. So what we have >> is a word that becomes more vague the larger the context is. >> >> Happily, that means that as one narrows the context, one also narrows >> down the possible meanings of "pointer". Narrowing it down to the >> pointers directly supported by the C++ language, the RAW POINTERS of >> C++, there is almost no ambiguity. In this very limited context the term >> is well-defined. >> >> Now, three questions that I have seen mentioned often in the debates, are >> >> 1) Is an array a pointer? >> >> 2) Can a pointer point to an array? >> >> 3) Can a pointer of type T* be said to point to an array of T? >> >> Regarding question (1), is an array a pointer?, the answer is NO. >> >> Some newbies think the answer is yes because lots of things are very >> much the same for pointers and arrays. But the crucial thing is not how >> operationally similar they are. Instead, the crucial thing is how they >> differ, for example that an array can occupy an arbitrary amount of >> storage, while the size of a pointer -- e.g. as reported by the sizeof >> operator -- is pretty small. >> >> Regarding question (2), can a pointer point to an array? >> >> Here the answer is YES, and, /in two different ways/. >> >> First, a pointer can point to an array in the Pascal sense, where the >> pointer is of type "pointer to array" and points to some array (or else >> is null), like >> >> int a[42]; >> int (*p1)[42] =&a; // OK, p1 is a pointer to array (type-wise). >> >> It would be wrong to omit the "42" in the pointer declaration, because >> p1 is very very strictly a pointer to an array *of a given size*. You >> would not be able to e.g. "++" increment the pointer if the pointee type >> was of some unknown size. And although you can have pointers to >> incomplete types (types of unknown size (uh, I mean, types whose >> instances are of unknown size (or, more pedantically, types whose >> instances, if they could exist, would be of unknown size (hm, ok, I >> direct you to the Holy Standard for absolute precision)))), in this >> specific case the language does not permit it -- I don't know why. >> >> So, in the case above we have a pointer variable that points to an >> array, *and* that is of type pointer to array. >> >> The second way in which a pointer can point to an array, is the answer >> to question 3, namely >> >> int a[42]; >> int* p2 = a; // OK, p2 is a pointer to an array (dynamically). >> >> In this case, however, the type of the pointer is not a pointer to >> array, but pointer to ElementType. It's only the dynamic situation that >> right after the above declaration, p2 points to array a. Still, this is >> the most common situation (the p1 thing is extremely rare!), and it >> would be silly to talk about "points, at this point in the program >> execution, to the first element of an array", sort of like a lawyer, >> instead of just saying "points to an array". >> > > Strictly speaking the above is a pointer to the first element of an > array. Note that I put back my last paragraph above, which you elected to move quite a bit away. The only reason I can think of why you're paraphrasing a bit from the paragraph that you moved away from the point where you put the paraphrase, apart from trolling, would be to seek confirmation of correct understanding. If so, then yes it seems that you roughly understood that. However, the formal does not address terminology except for the formal. And so the "strictly speaking" is, stricly speaking, noise, not a clarification (otherwise your understanding would appear to be perfect). > The code below is an example of a pointer to an array. > > int (*p3)[42] =&a; And here you're again repeating an example, just changing a name. Apparently you understood what that example was about. > But the confusion is understandable as the following array access using > the pointer is valid. You have apparently (disregarding the possibility of trolling) asked for confimation of your understanding of two points, that's OK, easy to deal with. But you have to also tell what you are (or someone is) confused about, when you start talking about your (or someone's) confusion. Your readers are not telepaths, and at least I cannot guess what you're talking about here -- the ESP circuit reports "no connection". Cheers & hth., - Alf -- blog at <url: http://alfps.wordpress.com>
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On generally accepted terminology for pointers and arrays "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-04-12 04:00 +0200
Re: On generally accepted terminology for pointers and arrays Pavel <pauldontspamtolk@removeyourself.dontspam.yahoo> - 2011-04-12 00:13 -0400
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-12 05:17 +0100
Re: On generally accepted terminology for pointers and arrays Leigh Johnston <leigh@i42.co.uk> - 2011-04-12 14:02 +0100
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-12 14:10 +0100
Re: On generally accepted terminology for pointers and arrays Leigh Johnston <leigh@i42.co.uk> - 2011-04-12 14:49 +0100
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-12 10:05 -0400
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-12 01:11 -0400
Re: On generally accepted terminology for pointers and arrays gwowen <gwowen@gmail.com> - 2011-04-11 23:24 -0700
Re: On generally accepted terminology for pointers and arrays gwowen <gwowen@gmail.com> - 2011-04-12 00:16 -0700
Re: On generally accepted terminology for pointers and arrays Leigh Johnston <leigh@i42.co.uk> - 2011-04-12 13:53 +0100
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-12 14:08 +0100
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-12 14:05 +0100
Re: On generally accepted terminology for pointers and arrays Leigh Johnston <leigh@i42.co.uk> - 2011-04-12 14:48 +0100
Re: On generally accepted terminology for pointers and arrays Ian Collins <ian-news@hotmail.com> - 2011-04-13 07:53 +1200
Re: On generally accepted terminology for pointers and arrays "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-04-12 22:14 +0200
Re: On generally accepted terminology for pointers and arrays Öö Tiib <ootiib@hot.ee> - 2011-04-12 15:39 -0700
Re: On generally accepted terminology for pointers and arrays Goran <goran.pusic@gmail.com> - 2011-04-12 01:39 -0700
Re: On generally accepted terminology for pointers and arrays Ian Collins <ian-news@hotmail.com> - 2011-04-12 20:51 +1200
Re: On generally accepted terminology for pointers and arrays Jorgen Grahn <grahn+nntp@snipabacken.se> - 2011-04-12 21:51 +0000
Re: On generally accepted terminology for pointers and arrays cpp4ever <n2xssvv.g02gfr12930@ntlworld.com> - 2011-04-12 09:59 +0100
Re: On generally accepted terminology for pointers and arrays "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-04-12 16:25 +0200
Re: On generally accepted terminology for pointers and arrays cpp4ever <n2xssvv.g02gfr12930@ntlworld.com> - 2011-04-12 16:07 +0100
Re: On generally accepted terminology for pointers and arrays "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-04-12 17:32 +0200
Re: On generally accepted terminology for pointers and arrays cpp4ever <n2xssvv.g02gfr12930@ntlworld.com> - 2011-04-12 16:53 +0100
Re: On generally accepted terminology for pointers and arrays "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-04-12 18:16 +0200
Re: On generally accepted terminology for pointers and arrays cpp4ever <n2xssvv.g02gfr12930@ntlworld.com> - 2011-04-12 17:39 +0100
Re: On generally accepted terminology for pointers and arrays "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-04-12 19:32 +0200
Re: DILLIGAF cpp4ever <n2xssvv.g02gfr12930@ntlworld.com> - 2011-04-12 19:05 +0100
Re: DILLIGAF Peter Remmers <p.remmers@expires-2011-04-30.arcornews.de> - 2011-04-12 20:36 +0200
Re: DILLIGAF cpp4ever <n2xssvv.g02gfr12930@ntlworld.com> - 2011-04-12 20:47 +0100
Re: DILLIGAF gwowen <gwowen@gmail.com> - 2011-04-12 14:48 -0700
Re: DILLIGAF Öö Tiib <ootiib@hot.ee> - 2011-04-12 15:16 -0700
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-12 17:48 +0100
Re: On generally accepted terminology for pointers and arrays Noah Roberts <dont@email.me> - 2011-04-12 09:37 -0700
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-12 18:34 +0100
Re: On generally accepted terminology for pointers and arrays "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-04-12 19:38 +0200
Re: On generally accepted terminology for pointers and arrays Noah Roberts <dont@email.me> - 2011-04-12 11:00 -0700
Re: On generally accepted terminology for pointers and arrays "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-04-12 20:03 +0200
Re: On generally accepted terminology for pointers and arrays Noah Roberts <dont@email.me> - 2011-04-12 11:06 -0700
Re: On generally accepted terminology for pointers and arrays Peter Remmers <p.remmers@expires-2011-04-30.arcornews.de> - 2011-04-12 20:26 +0200
Re: On generally accepted terminology for pointers and arrays Noah Roberts <dont@email.me> - 2011-04-12 11:33 -0700
Re: On generally accepted terminology for pointers and arrays Peter Remmers <p.remmers@expires-2011-04-30.arcornews.de> - 2011-04-12 20:55 +0200
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-12 20:14 +0100
Re: On generally accepted terminology for pointers and arrays Noah Roberts <dont@email.me> - 2011-04-12 12:47 -0700
Re: On generally accepted terminology for pointers and arrays Peter Remmers <p.remmers@expires-2011-04-30.arcornews.de> - 2011-04-12 22:40 +0200
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-12 14:15 -0400
Re: On generally accepted terminology for pointers and arrays "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-04-12 20:52 +0200
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-12 20:23 +0100
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-12 16:01 -0400
Re: On generally accepted terminology for pointers and arrays Noah Roberts <dont@email.me> - 2011-04-12 13:46 -0700
Re: On generally accepted terminology for pointers and arrays Öö Tiib <ootiib@hot.ee> - 2011-04-12 19:49 -0700
Re: On generally accepted terminology for pointers and arrays hanukas <jukka@liimatta.org> - 2011-04-13 00:06 -0700
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-13 04:14 -0400
Re: On generally accepted terminology for pointers and arrays Öö Tiib <ootiib@hot.ee> - 2011-04-13 07:53 -0700
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-13 09:52 +0100
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-13 05:20 -0400
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-13 10:31 +0100
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-13 07:04 -0400
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-13 12:35 +0100
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-13 07:41 -0400
Re: On generally accepted terminology for pointers and arrays Ian Collins <ian-news@hotmail.com> - 2011-04-14 07:47 +1200
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-14 11:44 +0100
Re: On generally accepted terminology for pointers and arrays "io_x" <a@b.c.invalid> - 2011-04-13 18:41 +0200
Re: On generally accepted terminology for pointers and arrays Noah Roberts <dont@email.me> - 2011-04-13 09:35 -0700
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-13 20:17 +0100
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-13 04:33 -0400
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-13 04:35 -0400
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-13 01:19 +0100
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-13 04:01 -0400
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-13 04:20 -0400
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-13 09:56 +0100
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-13 05:24 -0400
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-13 10:34 +0100
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-13 07:07 -0400
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-13 12:36 +0100
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-13 07:43 -0400
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-13 13:18 +0100
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-13 08:30 -0400
Re: On generally accepted terminology for pointers and arrays "Alf P. Steinbach /Usenet" <alf.p.steinbach+usenet@gmail.com> - 2011-04-13 15:57 +0200
Re: On generally accepted terminology for pointers and arrays Leigh Johnston <leigh@i42.co.uk> - 2011-04-13 15:10 +0100
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-13 11:09 -0400
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-13 12:04 -0400
Re: On generally accepted terminology for pointers and arrays Noah Roberts <dont@email.me> - 2011-04-13 09:56 -0700
Re: On generally accepted terminology for pointers and arrays cg_chas <cg_chas@hotmail.com> - 2011-04-13 14:11 -0400
Re: On generally accepted terminology for pointers and arrays "Paul" <pchristor@yahoo.co.uk> - 2011-04-12 19:29 +0100
Re: On generally accepted terminology for pointers and arrays Joshua Maurice <joshuamaurice@gmail.com> - 2011-04-12 09:36 -0700
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