From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=0.6 required=5.0 tests=BAYES_20,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: fac41,9a0ff0bffdf63657 X-Google-Attributes: gidfac41,public X-Google-Thread: 103376,4b06f8f15f01a568 X-Google-Attributes: gid103376,public X-Google-Thread: 1108a1,9a0ff0bffdf63657 X-Google-Attributes: gid1108a1,public X-Google-Thread: f43e6,9a0ff0bffdf63657 X-Google-Attributes: gidf43e6,public From: "Robert Martin" Subject: Re: Module size (was Re: Software landmines) Date: 1998/09/05 Message-ID: <6srhl8$spv$1@hirame.wwa.com>#1/1 X-Deja-AN: 388156623 References: <6snlos$bh6$1@hirame.wwa.com> <904912650snz@nezumi.demon.co.uk> <35EFFB78.21BBBED6@ksc.nasa.gov> <6spfvf$nun$1@hirame.wwa.com> <6spojo$8ir$1@uuneo.neosoft.com> <35f58f68.94311132@news.erols.com> <35F0BC05.61919244@s054.aone.net.au> X-MimeOLE: Produced By Microsoft MimeOLE V4.72.2106.4 Organization: WorldWide Access - Midwestern Internet Services - www.wwa.com Newsgroups: comp.lang.eiffel,comp.object,comp.software-eng,comp.lang.ada Date: 1998-09-05T00:00:00+00:00 List-Id: Loryn Jenkins wrote in message <35F0BC05.61919244@s054.aone.net.au>... >> Unfortunately in C++ even if the interface of 2 classes is the same >> they are not polymorphically substitutable for each other unless they >> both inherit from a common class. > >This is interesting that you say "unfortunately". If 2 classes *did* >have the same interface, why wouldn't you make them both inherit from an >abstract class that defines the interface? class Shape { public: virtual void Draw() = 0; // Draw shape on screen. } class Pump { public: virtual void Draw() = 0; // draw water from the pump. }; Here are two classes that appear to have the same interface. But that is just appearance. In reality they have completely different interfaces. In Smalltalk, there is a chance that you could send a Pump object to a window, and that the window would try to Draw it. In C++ that is not an option. There are costs and benefits to the static typing of C++. It affords a certainl level of protection at the cost of a certain level of flexibility. But static typing is certainly not "unfortunate". Robert C. Martin | Design Consulting | Training courses offered: Object Mentor | rmartin@oma.com | Object Oriented Design 14619 N Somerset Cr | Tel: (800) 338-6716 | C++ Green Oaks IL 60048 | Fax: (847) 918-1023 | http://www.oma.com "One of the great commandments of science is: 'Mistrust arguments from authority.'" -- Carl Sagan