From 4927091446942317273 X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news2.google.com!news2.google.com!newsfeed.stanford.edu!news.kjsl.com!news.alt.net!frodo.cs.rpi.edu!not-for-mail From: Hyman Rosen Newsgroups: comp.std.c++ Subject: Re: for-else: adding else to for loops Date: Wed, 12 Aug 2009 13:49:39 CST Organization: unknown Lines: 38 Sender: cppmods@cs.rpi.edu Approved: austern@google.com Message-ID: <49Dgm.141164$Qg6.41767@newsfe14.iad> References: <5d82cd6c-2a22-4dd7-8c7d-790b579533ea@d15g2000prc.googlegroups.com> <84af1815-994d-48d6-9c07-c8965bba0d01@b25g2000prb.googlegroups.com> NNTP-Posting-Host: netlab.cs.rpi.edu Content-Type: text/plain; charset=ISO-8859-1; format=flowed To: (Usenet) Return-Path: X-Original-Date: Wed, 12 Aug 2009 13:41:19 -0400 X-Submission-Address: std-c++@netlab.cs.rpi.edu Xref: g2news2.google.com comp.std.c++:1274 Jared Grubb wrote: I just thought I'd ask. Once you've seen the flow, it's hard to get out of your head when a use for it pops up! How about this variant? for (auto i = c.begin(); i != c.end(); ++i) if (condition(*i)) break; and // do this only if loop exited normally cout << "Condition never matched" << endl; or // do this only if loop never executed cout << "Empty container" << endl; For an empty container, the above code would execute both the 'and' part and the 'or' part, in the order they appear, but either part can have a 'break' statement to terminate further processing. The scope of any variables declared by the 'for' initialization expression extends through the 'and' and 'or' clauses. This syntax avoids any new keywords and is backwards-compatible. It applies equally to while loops (the 'or' statement is never executed for a do-while loop, naturally). And it has the same infelicitous bind-to-nearest behavior that 'else' does :-) If you want, you could require compound-statements for the 'and' and 'or' parts, as 'try' and 'catch' do. -- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@netlab.cs.rpi.edu] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ]