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=0.2 required=5.0 tests=BAYES_00,INVALID_MSGID, REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: fac41,b87849933931bc93 X-Google-Attributes: gidfac41,public X-Google-Thread: 109fba,b87849933931bc93 X-Google-Attributes: gid109fba,public X-Google-Thread: 1108a1,b87849933931bc93 X-Google-Attributes: gid1108a1,public X-Google-Thread: 114809,b87849933931bc93 X-Google-Attributes: gid114809,public X-Google-Thread: 103376,b87849933931bc93 X-Google-Attributes: gid103376,public From: "Norman H. Cohen" Subject: Re: Multiple Type Interfaces Date: 1997/01/28 Message-ID: <32EE6EF2.2487@watson.ibm.com>#1/1 X-Deja-AN: 212895509 references: <6PE5zLpF3RB@herold.franken.de> content-type: text/plain; charset=us-ascii organization: IBM Thomas J. Watson Research Center mime-version: 1.0 reply-to: ncohen@watson.ibm.com newsgroups: comp.lang.eiffel,comp.lang.ada,comp.lang.c++,comp.lang.smalltalk,comp.object x-mailer: Mozilla 3.0 (Win95; I) Date: 1997-01-28T00:00:00+00:00 List-Id: Dave Gibson wrote: > When Ada83 evolved into Ada95, the concept of multiple type components (packages) > survived, but was excluded when it came to OO-style (extendable) tagged types. Not true. It's perfectly possible for an Ada-95 package to provide two different tagged types. This might be done, for example, because the two types share parts of their (hidden) implementations. If a package provides two types, T1 and T2, you cannot declare a subprogram in the package that has both a controlling operand (i.e., a parameter or a function result) of type T1 and one of type T2, because it would not be obvious in this case which operand's tag should control dispatching. However, you can have one operand of type T1 (controlling dispatching) and one of type T2'Class (not controlling dispatching) or the other way around. -- Norman H. Cohen mailto:ncohen@watson.ibm.com http://www.research.ibm.com/people/n/ncohen