Path: news.daimi.aau.dk!jacobse
From: jacobse@daimi.aau.dk (Jacob Seligmann)
Newsgroups: comp.object,comp.lang.eiffel,comp.lang.sather,comp.lang.beta,comp.lang.modula3
Subject: Re: Cows, Hogs & Farms
Date: 9 Jan 1995 15:21:56 GMT
Organization: DAIMI, Computer Science Dept. at Aarhus University
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Message-ID: <3erkak$sm7@belfort.daimi.aau.dk>
References: <3eih36$94g@network.ucsd.edu> <1995Jan6.164948.4782@schbbs.mot.com> <1995Jan9.005627@hobbit>
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Mark S. Hathaway <hathawa2@marshall.edu> wrote:

> > or BETA's form:
> > 
> >   MONOCULTUREFARM
> >     (#   ANIMALT :< HERBIVORE
> >          attr livestock : @list (# eleT::ANIMALT #);
> >          attr foodstock : @list (# eleT::ANIMALT.FOODT #); 
> >     #)
> 
> [...]
> 
> Since "ANIMALT :< HERBIVORE" is inside the "(#" & "#)" enclosure I wouldn't
> guess you could create a MONOCULTUREFARM(COW).

But you can! In BETA, you would say

   MONOCULTUREFARM (# ANIMALT :: COW #)

to denote a subclass of MONOCULTUREFARM in which the virtual attribute
ANIMALT is further-bound to COW. That is, genericity is handled through
inheritance and virtuals alone - there is no special template mechanism
whatsoever!

Of course, this is only possible because BETA allows virtual types, not
just virtual methods. This is typical of how BETA offers only a few
basic mechanisms, but makes them powerful and orthogonal, so that they
can be combined to obtain a wide range of features for which most other
languages provide special mechanisms.

> It's not especially readable, is it?
> [...]
> Yes, the language should provide a way to express something.  That's why
> I cringe when I see syntax like BETA's.  :-)

The reverse sign of the minimalism coin, of course, is the need to use
more syntax to express a feature which is obtainable through a special
(nice-looking) construct in another language.

I agree that 

   MONOCULTUREFARM [COW] 

or even 

   MONOCULTUREFARM [ ANIMALT = COW ]

is easier to read than

   MONOCULTUREFARM (# ANIMALT :: COW #) 

However, when working with BETA, you quickly learn to recognize use
patterns such as the one above. It's not a big deal in practice, really.

Best regards,

/Jacob Seligmann
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