Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!rutgers!att!cbnewsl!dog
From: dog@cbnewsl.ATT.COM (edward.n.schiebel)
Newsgroups: comp.lang.c++
Subject: Re: What to do about generics and polymorphism in C++
Message-ID: <4731@cbnewsl.ATT.COM>
Date: 23 Mar 90 17:37:10 GMT
References: <16808@well.sf.ca.us>
Organization: AT&T Bell Laboratories
Lines: 42

From article <16808@well.sf.ca.us>, by nagle@well.sf.ca.us (John Nagle):
> 
>       Let's start a discussion about the problem of how to achieve
> generic objects (ones with types as parameters, at least at compile
> time) in C++.  Some possibilities:
> 
>       3.  Add compile-time generic facilities along the lines of those
> 	  in Ada to the language.  Provides similar functionality to
> 	  #2, with proper checking and diagnostics, but requires
> 	  a language change.
> 
This is my choice.  Although I am not at all familiar with Ada, I
assume you are refering to an implementation generics similar to 
parameterized types described by Bjarne in some paper I can't find right 
now.  It seems to me that parameterized types provide
the type saftey  (as opposed to using void*'s) and the 
run-time efficiency (vrs. types as first-class objects)
that makes the most sense within the C++ language.  C++'s contributors
have always taken these two concerns very seriously throughout the 
language's evolution, and I don't expect them to stop now.

I have used and written (with more or less success) generic types
based on the preprocessor and I must say that it is an interim solution
at best.  Nonetheless, the generic types created by that scheme are a 
fair approximation of pramaterized types, and I have come to rely on
that kind of capability.  

From the first Usenix C++ Workshop (my first real introduction to the 
language) to the last OOPSLA, and probably through this years Usenix
conference (see you there), all I have heard is "what about generics" 
"what about exception handling" "what about garbage collection"?  
I don't even want to get another garbage collection discussion started,
and between the other two, for my money,
I would like to see parameterized types implemented first.  I believe
they would be adopted and used by more programs much quicker
than exception handling and would provide the greatest benefit to
C++'s users.

	Ed Schiebel
	AT&T Bell Laboratories
	dog@cblph.att.com