C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  i++ or ++i efficient          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Radde Guest Posted: Fri Jul 29, 2005 8:12 am    Post subject: i++ or ++i efficient HI all, Which is more efficient i++ or ++i and why is it?? cheers.. Back to top Alf P. Steinbach Guest Posted: Fri Jul 29, 2005 8:32 am    Post subject: Re: i++ or ++i efficient * Radde: Quote: Which is more efficient i++ or ++i and why is it?? The FAQ is at <url: http://www.parashift.com/c++-faq-lite/>. -- A: Because it messes up the order in which people normally read text. Q: Why is it such a bad thing? A: Top-posting. Q: What is the most annoying thing on usenet and in e-mail? Back to top Earl Purple Guest Posted: Fri Jul 29, 2005 11:43 am    Post subject: Re: i++ or ++i efficient Alf P. Steinbach wrote: Quote: * Radde: Which is more efficient i++ or ++i and why is it?? The FAQ is at <url: http://www.parashift.com/c++-faq-lite/>. and this is the section you want: <url: http://www.parashift.com/c++-faq-lite/operator-overloading.html#faq-13.15 /> Back to top red floyd Guest Posted: Fri Jul 29, 2005 3:47 pm    Post subject: Re: i++ or ++i efficient Radde wrote: Quote: HI all, Which is more efficient i++ or ++i and why is it?? If you have to ask the question "why", then you don't understand the language enough to need to worry about it. "Premature optimization is the root of all evil." -- Hoare's Law Back to top red floyd Guest Posted: Fri Jul 29, 2005 3:51 pm    Post subject: Re: i++ or ++i efficient red floyd wrote: Quote: If you have to ask the question "why", then you don't understand the language enough to need to worry about it. "Premature optimization is the root of all evil." -- Hoare's Law To reply to my own post. Sorry, that sounded snarky. What I meant was: to worry about such things without seeing if its actually an issue is premature and irrelevant. If your code is so tight that the few microseconds difference between ++i and i++ is critical, then you should be understanding the language anyways. The difference between ++i and i++ is explained in any introductory C++ (or C) book. Note, the comment about a few microsecods applies unless you're dealing with user-defined objects, in which case you should *already* know the difference, having written both operators. Hence the snarky comment. Hoare's Law still applies, though. Back to top Alf P. Steinbach Guest Posted: Fri Jul 29, 2005 3:51 pm    Post subject: Re: i++ or ++i efficient * red floyd: Quote: "Premature optimization is the root of all evil." -- Hoare's Law When did Hoare grab the honor of being the one who said that, from Knuth? -- A: Because it messes up the order in which people normally read text. Q: Why is it such a bad thing? A: Top-posting. Q: What is the most annoying thing on usenet and in e-mail? Back to top red floyd Guest Posted: Fri Jul 29, 2005 3:53 pm    Post subject: Re: i++ or ++i efficient Alf P. Steinbach wrote: Quote: * red floyd: "Premature optimization is the root of all evil." -- Hoare's Law When did Hoare grab the honor of being the one who said that, from Knuth? I had always heard it was Hoare. Maybe it was Knuth. What do I know? I'm just a hack. It's still true. :) Back to top red floyd Guest Posted: Fri Jul 29, 2005 3:55 pm    Post subject: Re: i++ or ++i efficient red floyd wrote: Quote: . Hoare's Law still applies, though. Or, to make Alf happy (), Knuth's Law. Back to top Marcin Kalicinski Guest Posted: Fri Jul 29, 2005 5:13 pm    Post subject: Re: i++ or ++i efficient Quote: What I meant was: to worry about such things without seeing if its actually an issue is premature and irrelevant. If your code is so tight that the few microseconds difference between ++i and i++ is critical, then you should be understanding the language anyways. There will be not even a nanosecond difference, because the code generated for both cases is exactly the same for built-in types on all sensible compilers (unless return value is used of course). cheers, M. Back to top Vyacheslav Kononenko Guest Posted: Fri Jul 29, 2005 5:41 pm    Post subject: Re: i++ or ++i efficient Alf P. Steinbach wrote: Quote: * red floyd: "Premature optimization is the root of all evil." -- Hoare's Law When did Hoare grab the honor of being the one who said that, from Knuth? -- A: Because it messes up the order in which people normally read text. Q: Why is it such a bad thing? A: Top-posting. Q: What is the most annoying thing on usenet and in e-mail? From: http://en.wikipedia.org/wiki/Talk:C._A._R._Hoare The quotation has been attributed to Knuth because it was written by Knuth. It appears in his article Structured Programming with GO TO Statements that appeared in ACM Computing Surveys, Vol. 6, No. 4, December 1974, p. 268. A more complete version is: There is no doubt that the grail of efficiency leads to abuse. Programmers waste enormous amounts of time thinking about, or worrying about, the speed of noncritical parts of their programs, and these attempts at efficiency actually have a strong negative impact when debugging and maintenance are considered. We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. -- Dominus 14:27, 3 Dec 2004 (UTC) On further investigation, I find that Knuth does attribute the "premature optimization" aphorism to Hoare. (Although not, obviously, the particular statement of it quoted above.) See Knuth's 1989 paper The Errors of TeX, section F: (But I also knew, and forgot, Hoare's dictum that premature optimization is the root of all evil in programming.) -- Dominus 02:03, 4 Dec 2004 (UTC) Regards, Vyacheslav Back to top Naif Al-Dalbahi Guest Posted: Sun Jul 31, 2005 2:32 pm    Post subject: Re: i++ or ++i efficient when it comes to efficiency , both expression they have the same level Quote: but ++i means , increment i first then use it and i++ use the current value of i then increment it Back to top Stuart MacMartin Guest Posted: Mon Aug 08, 2005 1:06 pm    Post subject: Re: i++ or ++i efficient Beg to differ with other posters, but this depends on what "i" is. If it's a complex object, then ++i can be significantly faster than i++. Stuart Back to top Vijai Kalyan Guest Posted: Mon Aug 08, 2005 7:13 pm    Post subject: Re: i++ or ++i efficient Well, actually, it _was_ Knuth I believe who said that. -vijai. Back to top red floyd Guest Posted: Mon Aug 08, 2005 8:02 pm    Post subject: Re: i++ or ++i efficient Vijai Kalyan wrote: Quote: Well, actually, it _was_ Knuth I believe who said that. -vijai. See Vyacheslav Kononenko's response to that: <http://groups-beta.google.com/group/comp.lang.c++/tree/browse_frm/thread/5973d9c8aab298dc/9c381c6ae83b014e?rnum=1&hl=en&_done=%2Fgroup%2Fcomp.lang.c%2B%2B%2Fbrowse_frm%2Fthread%2F5973d9c8aab298dc%2F9c381c6ae83b014e%3Ftvc%3D1%26#doc_0009507da3eb30f4> Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ language (comp.lang.c++) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.