From 6777036938767713880 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: f78e5,df0f8d484c0311f9,start X-Google-Attributes: gidf78e5,public Path: controlnews3.google.com!news2.google.com!news.maxwell.syr.edu!newsfeed.icl.net!newsfeed.fjserv.net!kibo.news.demon.net!mutlu.news.demon.net!demon!mail2news.demon.co.uk!devnull From: meang@post.com (Meang Akira Tanaka) Newsgroups: comp.std.c++ Subject: Proposal for default values when declaring the class Date: Fri, 30 Apr 2004 03:14:25 +0000 (UTC) Organization: UNI2 Internet Kunde Lines: 113 Approved: fjh@cs.mu.oz.au (Fergus Henderson , moderator of comp.std.c++) Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: mail2news.demon.co.uk 1083294865 12749 10.0.0.1 (30 Apr 2004 03:14:25 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Fri, 30 Apr 2004 03:14:25 +0000 (UTC) X-Received: from mulga.cs.mu.oz.au ([128.250.1.22]) by news.demon.co.uk with esmtp (Exim 4.12) id 1BJOTp-0003JU-00 for mail2news@news.news.demon.net; Fri, 30 Apr 2004 03:14:25 +0000 X-Received: from mulga.cs.mu.OZ.AU (localhost [127.0.0.1]) by mulga.cs.mu.OZ.AU with ESMTP id i3U3ELi2016725; Fri, 30 Apr 2004 13:14:21 +1000 (EST) X-Received: (from fjh@localhost) by mulga.cs.mu.OZ.AU (8.12.10+Sun/8.12.9/Submit) id i3U3ELdm016716; Fri, 30 Apr 2004 13:14:21 +1000 (EST) X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Path: comp-std-cpp-robomod!not-for-mail X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-Delivered-To: std-c++@ucar.edu X-Newsgroups: comp.std.c++ X-Newsreader: Forte Agent 1.93/32.576 English (American) X-NNTP-Posting-Date: Wed, 28 Apr 2004 22:59:23 CEST X-Spam-Level: X-Spam-Checker-Version: SpamAssassin 2.60-mulga_r1 (1.212-2003-09-23-exp) on mulga.cs.mu.OZ.AU X-Spam-Status: No, hits=0.0 required=5.2 tests=none autolearn=no version=2.60-mulga_r1 Xref: controlnews3.google.com comp.std.c++:20 Hi It may not be the right forum but I would like to make a proposal. (if this is not the right forum could anybody please tell me which forum this should be be submitted too) In my experience with programming C++. I have wondered why it hasn't been possible to define default values in the class declaration. One had to do it in the constructor. e.g. class foo { int mVar1; bool mVar2; char mVar3; foo() : mVar1(100), mVar2(true), mVar3('a') { } foo(int newVar1) : mVar1(newVar1), mVar2(true), mVar3('a') { } foo(bool newVar2) : mVar1(105), mVar2(newVar2), mVar3('a') { } } The disadvantage with the current approach is manyfold. 1. One has to define the initial value for all or some of the member variables again and again for each declared constructor. Typically the values which has not been assigned a value explicitly, they typically have the same value no matter which constructor was invoked. 2. When someone is adding an another constructor to the class. They have to make sure that all the variables have been initialized. In an idealistic world everybody would probably remember to do it, however I claim this is not the case in the real world. 3. If the class is added with a new attribute, one has to ensure that all the constructors do initialize the value. I propose that one can do the following: class foo { int mVar1 = 100; bool mVar2 = true; char mVar3 = 'a'; foo() { } foo(int newVar1) : mVar1(newVar1) { } foo(bool newVar2): mVar1(105), mVar2(newVar2) { } } The difference between this and the current implementation of the standard is the variable is assigned to a value. if it isn't overriden in the constructor. What are the advatanges? Well... If the an initial value is given, then they don't need to be defined for all the new constructor actually needs to assign it to another value. This ensures that the instant has a sane or at least a more sane value than some value in memory. if an instance is invoked with default constructor then the member attributes has the following value: mVar1 = 100; mVar2 = true mVar3 = 'a' if an instance is invoked with the second constructor then the member attributes has the following value: mVar1 = newVar1 mVar2 = true mVar3 = 'a' if an instance is invoked with the second constructor then the member attributes has the following value: mVar1 = 105 mVar2 = newVar2 mVar3 = 'a' The mVar is overriden with 105 br Meang --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ]