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From: milne@ics.uci.edu (Alastair Milne)
Newsgroups: comp.lang.misc,comp.lang.pascal
Subject: Re: OOP features in Turbo Pascal 5.5
Message-ID: <15150@paris.ics.uci.edu>
Date: 20 May 89 02:18:10 GMT
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grs@wucs1.wustl.edu (Guillermo Ricardo Simari) writes
>Any comments about the OOP features in Turbo Pascal 5.5
>and Quick Pascal of Microsoft?
  
     Turbo Pascal 5.5?  Last one I knew of was 5.0 .  Is this a simple typo,
     or have a I missed an announcement from Borland?  

     I don't know of "Quick Pascal".  The only Pascal I know of from Microsoft
     is, as you would expect, MS Pascal.

     As in UCSD Pascal, Turbo 4, Mac Pascal, Modula-2, etc. the unit construct
     can be used quite effectively for creating a certain degree of object
     orientation -- though I would probably continue to prefer the term
     "abstract data types", since the unit feature doesn't directly support 
     such features as message passing -- if it's going to happen, it must be
     of the programmer's creation.  Nor do you have such properties as
     inheritance: rather, if you export a new type, you can also export
     routines which apply exclusively to objects that the client declares to
     be of that type.

     So how effective units are for object-orientation really depends rather 
     heavily on how cleanly the programmer defines the interface of the unit 
     -- types to be exported, operations to be exported for them -- and 
     it can be as easy to export an inconsistent, unsecure, half-supported 
     mess as to export a solid, seamless, fully-functional new data type.  
     The syntax doesn't provide quite the guidance (or power) of, say, 
     Ada packages.  

     Units, of course, have quite a number of other advantages, especially if
     you know how to use them well.  The list could run to a fair-sized essay,
     which I won't try to do here.


     Alastair Milne