From 1434890860566975819 X-Google-Thread: 7894ca11fe,d47b345505a72a70 X-Google-Attributes: gid7894ca11fe,public,usenet X-Google-NewGroupId: yes X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news2.google.com!news1.google.com!news.glorb.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: Mon, 17 Aug 2009 13:18:48 CST Organization: unknown Lines: 31 Sender: cppmods@cs.rpi.edu Approved: stephen.clamage@sun.com Message-ID: References: <5d82cd6c-2a22-4dd7-8c7d-790b579533ea@d15g2000prc.googlegroups.com> <9e9c2ca5-78eb-460c-adec-2ec051c54210@r18g2000yqd.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: Sun, 16 Aug 2009 13:33:58 -0400 X-Submission-Address: std-c++@netlab.cs.rpi.edu Xref: g2news2.google.com comp.std.c++:1305 James Kanze wrote: > But throwing in an else without knowing what the "if" is > definitely destroys the readability. You repeat the test or use > the added boolean variable so that the reader can see what the > test is---otherwise, he's fully in the dark. A language construct has a defined meaning. Why would a reader be in the dark about it? My suggestion to augment loops was for (init; test; next) SL or SO and SA while (test) SL or SO and SA do SL while(test); and SA where a missing 'or' or 'and' part is taken to be there with a null statement. SO is executed if 'test' is false the first time it is evaluated. SA is executed if 'test' is ever false when evaluated. A 'break' in SL, SO, or SA moves control past the entire construct. Variables in the 'init' statement are in scope in SO and SA. Because of the semantics of the 'or' and 'and' parts, execution of SO falls into execution of SA, which is a nice touch. This cleanly distinguishes between loops having empty ranges, loops exhausting their ranges, and loops exited early. What's dark about it? -- [ 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 ]