tag:blogger.com,1999:blog-17885055.post4131892205849324539..comments2008-02-08T23:58:09.178+01:00Julio Merinohttp://www.blogger.com/profile/08233346614736256024noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-17885055.post-26606363262830601962008-02-08T23:58:00.000+01:002008-02-08T23:58:00.000+01:00Yeah, I ran into the same problem while working on a school project. It definitely caught me off guard.<BR/><BR/>This is fun, you should do it more often :)Johnhttp://www.blogger.com/profile/14829017628725137647noreply@blogger.comtag:blogger.com,1999:blog-17885055.post-30381024034697048002008-02-08T23:42:00.000+01:002008-02-08T23:42:00.000+01:00John: Bingo!<BR/><BR/>This piece of code bothered me this morning for a while until I came to this same conclusion. I assumed it had to work because it surely does when you use, for example, a vector instead of a set, but when you think about it you realize it cannot work :-)Julio M. Merino Vidalhttp://www.blogger.com/profile/08233346614736256024noreply@blogger.comtag:blogger.com,1999:blog-17885055.post-21502031908624789532008-02-08T23:09:00.000+01:002008-02-08T23:09:00.000+01:00The reason why *iter is read only is because the elements in the set are also keys. If you were able to modify *iter, then you run the risk of having two or more of the same key.<BR/><BR/>Also, the elements are sorted (I think), so modifying *iter would mean the set would have to sort itself after every iteration.Johnhttp://www.blogger.com/profile/14829017628725137647noreply@blogger.comtag:blogger.com,1999:blog-17885055.post-18223071015433117352008-02-08T22:51:00.000+01:002008-02-08T22:51:00.000+01:00Well, this is surprise for me as well, but seems that iterator type doesn't have to be mutable.<BR/><BR/>I don't have the ISO standard by hand, but SGI STL documentation says that for Container, X::iterator must be an 'input iterator', which is not required to be mutable.lrrrhttp://www.blogger.com/profile/12742106367384624657noreply@blogger.comtag:blogger.com,1999:blog-17885055.post-9523237638001700842008-02-08T22:04:00.000+01:002008-02-08T22:04:00.000+01:00John: Exactly, that's why it fails.<BR/><BR/>Now the real question is: why is *iter read-only if the code is using an iterator and not a const_iterator?Julio M. Merino Vidalhttp://www.blogger.com/profile/08233346614736256024noreply@blogger.comtag:blogger.com,1999:blog-17885055.post-66433809514659782492008-02-08T19:50:00.000+01:002008-02-08T19:50:00.000+01:00The problem comes with i++ in your second for loop.<BR/><BR/>Since i is an int& and you assigned it *iter, it is the same as using *iter. *iter is read only, so that is why the increment breaks the build.<BR/><BR/>Just a guess :)Johnhttp://www.blogger.com/profile/14829017628725137647noreply@blogger.comtag:blogger.com,1999:blog-17885055.post-73705859869703716982008-02-08T19:21:00.000+01:002008-02-08T19:21:00.000+01:00Julio! You should know... you are missing the 'include' and the 'main' XD<BR/><BR/>C++ is sometimes too weird...Lluisnoreply@blogger.com