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From: rogoff@Lanczos.Stanford.EDU (Brian Rogoff)
Newsgroups: comp.lang.beta
Subject: Re: Value patterns in BETA?
Date: 14 Feb 95 13:12:12
Organization: /u/rogoff/.organization
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References: <ROGOFF.95Jan31183456@sccm.Stanford.EDU> <3gsak5$j5b@engnews2.Eng.Sun.COM>
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In-reply-to: olevi@daimi.aau.dk's message of 13 Feb 1995 15:08:11 GMT

In article <3hnskr$13m@belfort.daimi.aau.dk> olevi@daimi.aau.dk (Ole Villumsen) writes:
   Brian Rogoff <rogoff@sccm.Stanford.EDU> writes:
   >I asked about this some time ago, and I was told that there is indeed a tag 
   >in Mjolner BETA. Is this the case?

   Yes: there is a small space overhead for every object in a BETA
   program. There is no *time* penalty, as far as I know.

More on this later in the article. Ole and I exchanged a few e-mails on this, 
parts of which I'll include (with his permission) below.

   >In article <3gsak5$j5b@engnews2.Eng.Sun.COM> olm@Eng.Sun.COM (Ole Lehrmann Madsen) writes:

   >	   p1 -> p2.add -> p3

   >   but if you mean operator overloading like

   >	   p1 + p2 -> p3

   I'd prefer  (p1,p2) -> add -> p3 , which is possible in BETA.

That's fine, as long as all of the basic numeric patterns use the same names. 

   >That wasn't part of my original question, but your prescience is amazing 
   >because I was wondering about that too! I agree that real overloading may 
   >be kind of heavy for BETA, but how about some kind of Eiffel 3 style 
   >ability to declare new binary operators without ad-hoc polymorphism? I 

   Not knowing Eiffel 3, I can't answer your question here.

I was just thinking that the syntactic sugar of being able to make up infix 
operators would be nice, even if it were not accompanied by "ad-hoc" 
polymorphism, which can also be nice for scientific programming

   --
   Ole Villumsen, Computer Science Department, Aarhus University, Denmark
   - no, not *that* Ole :-)   "When God created time, he created enough of it."


In an e-mail message Ole writes, in response to my query about whether 
the small space overhead occurs once per "Matrix of MyComplex" or for 
every "MyComplex" in the Matrix:

   But I'll have to disappoint you: the penalty comes with *each object*. I
   think it's 16 bytes or so - I never understood why it had to be so much;
   but I could be wrong about the amount. No way I know of to "untag" patterns
   or objects, except hand-build the data structure using only basic types.
   There is no penalty with those (integer, real, boolean, char). I'll
   elaborate in the news.

   Ole

That is too much. A "Matrix of MyComplex" is 3 times as big as it needs to 
be (assuming 2 4 byte floats for the complex and a tagless reresentation).

I am willing to surrender some flexibility and extensibility for speed and 
space. I believe that it is possible to have at least some amount of genericity, 
i.e., to be able to write a generic NumericMatrix, and not have to have 
tags if I am willing to surrender the ability to do OO dispatch on the type.

-- Brian