Stylistic questions on UNIX C coding.
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From: Richard Heathfield on 6 Mar 2010 04:07 Seebs wrote: > On 2010-03-06, Richard Heathfield <rjh(a)see.sig.invalid> wrote: >> No, he isn't. :-) Anyone who wastes half a day on understanding 7==x is >> not the kind of person you want maintaining C code in the first place. > > Not "understanding 7==x". Figuring out whether it's been done that way for > a particular reason. If it takes him more than a quarter of a second to recognise that the writer put the constant on the left to allow even the dumbest of compilers to alert the programmer in case he missed one of the =s (given that this technique is hardly a trade secret), then he's not the kind of person you want maintaining C code in the first place. > And while "half a day" may be a bit much, I've certainly > seen fairly experienced coders lose an hour or more to something that was > written in a way that suggested a deeper meaning or intent when it was, in > fact, merely idiosyncratic. > > If someone wrote: > for (i = 0; max > i; ++i) > I'd at least want to investigate briefly whether there was some non-obvious > reason for which the comparison was written backwards. You say it's "backwards", and okay, obviously I believe that you see it that way. I /don't/ see it that way. <shrug> <snip> -- Richard Heathfield <http://www.cpax.org.uk> Email: -http://www. +rjh@ "Usenet is a strange place" - dmr 29 July 1999 Sig line vacant - apply within
From: Seebs on 6 Mar 2010 04:47 On 2010-03-06, Richard Heathfield <rjh(a)see.sig.invalid> wrote: > Seebs wrote: >> Not "understanding 7==x". Figuring out whether it's been done that way for >> a particular reason. > If it takes him more than a quarter of a second to recognise that the > writer put the constant on the left to allow even the dumbest of > compilers to alert the programmer in case he missed one of the =s (given > that this technique is hardly a trade secret), then he's not the kind of > person you want maintaining C code in the first place. I disagree. I wouldn't trust someone who made that assumption without checking it -- at least, say, verifying that the same author did that consistently. I've heard of that convention, and that argument for it, but I've never seen it actually solve a problem -- I don't think I've used a compiler in either of the last two decades that couldn't catch such errors in other ways. So if I see code written that way, I check it out to see whether that's what's up. That takes a lot more than a quarter second -- and if only one test in a file is written that way, I'm not going to assume it was someone using that convention, because if they did, all the other tests would be the same. >> If someone wrote: >> for (i = 0; max > i; ++i) >> I'd at least want to investigate briefly whether there was some non-obvious >> reason for which the comparison was written backwards. > You say it's "backwards", and okay, obviously I believe that you see it > that way. I /don't/ see it that way. <shrug> That's fine -- but since the vast majority of code writes those relations in a consistent way, exceptions ought to be looked at. Cases where something is done in an unusual way are often either errors or signs of something funky up with the code. -s -- Copyright 2010, all wrongs reversed. Peter Seebach / usenet-nospam(a)seebs.net http://www.seebs.net/log/ <-- lawsuits, religion, and funny pictures http://en.wikipedia.org/wiki/Fair_Game_(Scientology) <-- get educated!
From: io_x on 6 Mar 2010 05:10 "pete" <pfiland(a)mindspring.com> ha scritto nel messaggio news:4B919F04.271C(a)mindspring.com... > Richard Heathfield wrote: >> >> pete wrote: >> <snip> >> >> > To count down through an array with N elements, I use >> > >> > size_t i = N; >> > >> > while (i-- != 0) { >> > array[i]; >> > } >> >> Isn't this where we came in? Or was that another thread? > > I remember writing the same thing once a few weeks ago > but I don't remember which thread. the thread i would like to prove above is not ok but see i make wrong and i sent nothing > -- > pete
From: Lorenzo Villari on 6 Mar 2010 08:50 On 5 Mar 2010 23:29:45 +0100 lacos(a)ludens.elte.hu (Ersek, Laszlo) wrote: > No, I would not have picked up the "7 == x" style in that case. > > For example, Pascal has := for assignment and = for equality > (IIRC :)). Even in C, I started out with "x == 7". I was > occasionally bitten by "if (x = 7)" typos. Not very frequently, and > most of the time caught by compiler warnings. However, on some forum > somebody brought up "7 == x" explicitly, and after giving the idea my > unrelenting attention :) for a minute or two, I liked it so much that > I trained myself to it. 1) The "Even in C" is in one some way related to "For example, Pascal..." ? 2) The fact you "liked it so much" has something to do with Pascal? I prefer if (x == 7) because it gives me the idea I'm testing x more and because 90 % of the code I've seen use that.
From: Ersek, Laszlo on 6 Mar 2010 11:16
In article <20100306145059.04e9465c(a)kubuntu>, Lorenzo Villari <vlllnz(a)tiscali.it> writes: > On 5 Mar 2010 23:29:45 +0100 > lacos(a)ludens.elte.hu (Ersek, Laszlo) wrote: > >> No, I would not have picked up the "7 == x" style in that case. >> >> For example, Pascal has := for assignment and = for equality >> (IIRC :)). Even in C, I started out with "x == 7". I was >> occasionally bitten by "if (x = 7)" typos. Not very frequently, and >> most of the time caught by compiler warnings. However, on some forum >> somebody brought up "7 == x" explicitly, and after giving the idea my >> unrelenting attention :) for a minute or two, I liked it so much that >> I trained myself to it. > > 1) The "Even in C" is in one some way related to "For example, > Pascal..." ? I guess I did some fairly bad editing with the above :) 1. The question was if people liking "7 == x" would stick to it if the language had an assignment operator that couldn't easily be mixed up with testing for equality. 2. No, I would not stick to it then. For example, in Pascal, where the assignment operator ":=" resembles the mathematical "let ... be" (define .... as) act and is intuitively different from testing for equality, and also where you can't put an assignment into a controlling expression anyway, I never felt the need to write 7 == x (or rather, in Pascal, 7 = x). Pascal is an example for the kind of language Keith specified in 1. (You snipped the original question so I write this from memory.) 3. Even in C, where I later found "7 == x" useful, it was not part of my original style. Thus: Pascal -- no motivation, C -- even though I discovered my incentive later, the idea was not obvious and didn't match my initial way of writing ==. The word "even" refers to the fact that Pascal bears no such incentive for me, while C does. (Perhaps it's even more confusing now, sorry.) > 2) The fact you "liked it so much" has something to do with Pascal? No, it has not. Cheers, lacos |