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From: alfh@byleist.ifi.uio.no (Alf-Ivar Holm)
Newsgroups: comp.lang.beta
Subject: Re: Pattern variables
Date: 14 Feb 1995 11:10:37 GMT
Organization: Dept. of Informatics, University of Oslo, Norway
Lines: 47
Message-ID: <ALFH.95Feb14121037@byleist.ifi.uio.no>
References: <ALFH.95Feb6184811@byleist.ifi.uio.no> <agesen.792543726@Xenon.Stanford.EDU>
NNTP-Posting-Host: byleist.ifi.uio.no
In-reply-to: agesen@Xenon.Stanford.EDU's message of 11 Feb 95 23:02:06 GMT
CC: 

In article <agesen.792543726@Xenon.Stanford.EDU> agesen@Xenon.Stanford.EDU (Ole Agesen) writes:

In article <agesen.792543726@Xenon.Stanford.EDU> agesen@Xenon.Stanford.EDU (Ole Agesen) writes:

> Regarding the specific example, I don't think any one construct is
> THE thing to use. Perhaps if your functions were more complicated than
> just x+x and x*x, perhaps if they had state, perhaps if it was a more
> complicated operator than simple composition, maybe one that evaluted
> the functions several times, perhaps then one or the other 
> representation would be "better". 
> 
> What does "better" mean here? Or more generally why is it necessary 
> (or rather desirable) to have pattern variables in Beta? Can't we 
> just always use dynamic object references, say? 
> 
> Yes, probably. But then we could also "just" program Turing machines.
> When designing a language, an important goal is to be able to express
> direct, extensible, maintainable, concise solutions to problems and at
> the same time avoid having a large complicated language. 
> Orthogonal concepts and few restrictions on how they can be combined is
> the established way to achieve the goal. For example: 
>       - We want static and dynamic references. 
>       - We want references to patterns and to objects. 
> Now, should references to patterns be restricted to being static? 
> Of course not.

I am not of the opinion of not wanting pattern variables in Beta.  I
just wanted to know if this particular example had some specific
"property" that made dynamic pattern references more appropriate than
dynamic object references.

I do like Beta because it is a small (syntacticly), but expressive and
powerful language.  By swapping functions, procedures, and classes
with patterns it has opened up new possibilities.  There are a lot of
ways to solve the same problem in Beta, which is a good thing, but it
also urges the programmer to _think_ about the design of a program, to
make it "good".  "Structured programming" in OO-languages has a lot do
to with mind set, since we are working on a higher level (than
non-OO-languages).  But, then again, I would guess that some language
constructs are more appropriate than others for certain type of
problems, and it is here that I am trying to fit pattern variables
into this.

(I just want to adopt a nice programming style in Beta, and it needs
some thought (and experience).)

	Affi