From -2132609240777633037 X-Google-Thread: f78e5,f6130266038a8c4d,start X-Google-Attributes: gidf78e5,public X-Google-Language: ENGLISH,ASCII-7-bit Path: g2news1.google.com!news1.google.com!news.glorb.com!fr.ip.ndsoftware.net!proxad.net!proxad.net!194.159.246.34.MISMATCH!peer-uk.news.demon.net!kibo.news.demon.net!news.demon.co.uk!demon!stump.algebra.com!devnull From: ben04_01@freenet.de (Ben Strasser) Newsgroups: comp.std.c++ Subject: Private Methodes declared outside of the class Date: Mon, 16 Aug 2004 14:48:32 GMT Lines: 71 Sender: mail2news@demon.net Approved: fjh@cs.mu.oz.au (Fergus Henderson , moderator of comp.std.c++) Message-ID: <2oblfaF8nds3U1@uni-berlin.de> NNTP-Posting-Host: news.news.demon.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Trace: news.demon.co.uk 1092667723 27551 158.152.254.254 (16 Aug 2004 14:48:43 GMT) X-Complaints-To: abuse@demon.net NNTP-Posting-Date: Mon, 16 Aug 2004 14:48:43 +0000 (UTC) X-Robomod: STUMP, ichudov@algebra.com (Igor Chudov) X-User-Agent: Mozilla Thunderbird 0.7.3 (Windows/20040803) X-Spam-Checker-Version: SpamAssassin 2.60-mulga_r1 (1.212-2003-09-23-exp) on mulga.cs.mu.OZ.AU X-Orig-X-Trace: news.uni-berlin.de LFbH46K4nNDkfkAgL7GYfg9pUwdLQX7zp3iA5jcim9U/5KpbHn X-Spam-Status: No, hits=-4.2 required=5.2 tests=BAYES_00,FROM_ENDS_IN_NUMS autolearn=no version=2.60-mulga_r1 X-Accept-Language: en-us, en X-Received: (from fjh@localhost) by mulga.cs.mu.OZ.AU (8.12.10+Sun/8.12.9/Submit) id i7GEmWN1001068; Tue, 17 Aug 2004 00:48:32 +1000 (EST) X-Path: comp-std-cpp-robomod!not-for-mail X-Spam-Level: X-Delivered-To: std-c++@ucar.edu X-Authentication-Warning: mulga.cs.mu.OZ.AU: fjh set sender to devnull@stump.algebra.com using -f X-Newsgroups: comp.std.c++ Xref: g2news1.google.com comp.std.c++:1723 Hello, I was wondering why you can not declare private methods outside of the class declaration? When you write a C like interface, you declare the functions inside a header and implement them inside a compilation unit. These functions may get big and therefore it's a good idea to spilt them up into a few helper functions. These helpers are not part of the interface and therefore they are often static or in a namespace{} block. If the implementation of the functions change, some helper functions may no longer be needed or new ones are added. This is no problem because they are not declared in the header and therefore no other compilation units knows about them and therefore do not need to be recompiled. Now when you are writing a C++ like interface (meaning a class) you put the declaration of the class and it's members inside the header. If they are public or protected they need to be there because those members are part of the interface. Private members are not part of the interface but part of the implementation, so other compilation units shouldn't know about them. They although have to know about data members because they need to know the total size of the class. Private methods although don't affect the size, so why are they there. There are few situation where they have to be in the header. For example if they are virtual, or a friend of the class uses them or when a public inline method uses them. But what about plain ordinary helper methods for plain ordinary public methods which are defined in the implementation unit? These don't have to be known in each compilation unit that includes the header. They even force recompilation when one is not needed. If the implementation of a class is changed but the data members, the public and protected methods stay the same then there is no need to recompile every unit that uses that class. If the implementation changes it is likely that new other helper methods are needed, these although are declared in the header so the header file has to be changed. Now the date of the last modification to the header file is changed and when compiling again, the compiler will think that the class has really been changed (because of the date of the header file) and recompile everything that includes that header. So why not allow something like: //header class A{ public: void do_stuff(); }; //cpp void A::helper(){ //... } void A::do_stuff(){ //... helper(); //... } helper has not been declared in the declaration of A so it is automatically assumed to be private. This wouldn't allow to break into the class in an other compilation unit, you can declare and define a private method everywhere although you can only call it from a protected / public method which has to be declared in the class declaration. --- [ 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 ]