C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Quick question...          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message deancoo Guest Posted: Fri Feb 25, 2005 6:17 am    Post subject: Quick question... If I have a container, say a vector, with 5 elements, and I initialize iterator variables to point to the beginning and end of the container, are those iterators going to always be valid if I replace the elements of the container? The size stays the same. It seems to be working now, but I thought I read somewhere something about this not always working out. Any thoughts? d Back to top Alf P. Steinbach Guest Posted: Fri Feb 25, 2005 7:02 am    Post subject: Re: Quick question... * deancoo: Quote: If I have a container, say a vector, with 5 elements, and I initialize iterator variables to point to the beginning and end of the container, are those iterators going to always be valid if I replace the elements of the container? The size stays the same. It seems to be working now, but I thought I read somewhere something about this not always working out. Any thoughts? Replacement is OK, insertion or deletion is not. -- 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 Thomas Maier-Komor Guest Posted: Fri Feb 25, 2005 9:01 am    Post subject: Re: Quick question... Alf P. Steinbach wrote: Quote: * deancoo: If I have a container, say a vector, with 5 elements, and I initialize iterator variables to point to the beginning and end of the container, are those iterators going to always be valid if I replace the elements of the container? The size stays the same. It seems to be working now, but I thought I read somewhere something about this not always working out. Any thoughts? Replacement is OK, insertion or deletion is not. yes, but only for a vector. a map or set will resort its content and therefore invalidate iterators... -- ________________________________________________________________________ Dipl.-Ing. Thomas Maier-Komor http://www.rcs.ei.tum.de Institute for Real-Time Computer Systems (RCS) fon +49-89-289-23578 Technische Universitaet Muenchen, D-80290 Muenchen fax +49-89-289-23555 Back to top Alf P. Steinbach Guest Posted: Fri Feb 25, 2005 9:48 am    Post subject: Re: Quick question... * Thomas Maier-Komor: Quote: Alf P. Steinbach wrote: * deancoo: If I have a container, say a vector, with 5 elements, and I initialize iterator variables to point to the beginning and end of the container, are those iterators going to always be valid if I replace the elements of the container? The size stays the same. It seems to be working now, but I thought I read somewhere something about this not always working out. Any thoughts? Replacement is OK, insertion or deletion is not. yes, but only for a vector. a map or set will resort its content and therefore invalidate iterators... Nope. However, you're right the OP wrote "container", I didn't see that. In general the question's answer depends on the container, that's why I didn't see that (like, if I have a hungry animal, say a dog that's got no food for three days, will it eat a raw steak?). My imaging system has powerful nonsense-filtering built-in... ;-) For associative containers, that's maps and sets: §23.1.2/8: "The insert members shall not affect the validity of iterators and references to the container, and the erase member shall invalidate only iterators and references to the erased elements." There is no resorting requirement, and if resorting takes place §23.1.2/8 restricts its effect on iterators and references. Replacement for an associative container is to replace the value of a pair, not the key (which cannot be replaced), and that does not affect iterators or references. Replacement for a vector or list or queue (not only vector) does not effect iterators and references. In short, value replacement is OK (unless one argumentatively regards swap as a replacement), insertion and deletion depends on the container in question. -- 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 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.