Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!pt.cs.cmu.edu!sei!ajpo!eberard
From: eberard@ajpo.sei.cmu.edu (Edward Berard)
Newsgroups: comp.object
Subject: Re: Evaluating "Object-Oriented" Programming Languages
Summary: clarifications
Keywords: object-oriented, programming languages, evaluation, bibliography
Message-ID: <649@ajpo.sei.cmu.edu>
Date: 11 Jan 90 15:30:43 GMT
References: <638@ajpo.sei.cmu.edu> <706@cui.unige.ch> <644@ajpo.sei.cmu.edu> <753@cui.unige.ch>
Lines: 80

In article <753@cui.unige.ch>, anders@cui.unige.ch (BJORNERSTEDT Anders) writes:
[...]
> Anyway I don't want to get into a useless debate on the differences and merits
> of Simula and Smalltalk. I was mainly concerned with the history of
> "oo-concepts", and strong typing. When you say
> that there are "missing" features in Simula which some regard as essential
> to an object-oriented language, I would be interested in hearing what
> those features are. Not because I want to enter the black hole of 
> how we should define "OO", but because I suspect that many people
> are not familiar with Simula and possibly do not understand what 
> features it has.

Like yourself, I have no interest in such a "useless debate."  Until
now, I was quite happy to say that some in the object-oriented
community considered Smalltalk to be the first "true" object-oriented
programming language, and these many of these same people considered
Simula an "immediate precursor" to object-oriented programming
languages.

However, this conversation has made me re-think my viewpoint.
Specifically, having re-examined my Simula and Smalltalk texts, I tend
to agree with you. While I would still argue that the term
"object-oriented" seems to have originated in the Smalltalk efforts,
that does _not_ mean that any programming language which pre-dates
Smalltalk is not "truly object-oriented."

I too, would be interested in hearing from anyone with a different
viewpoint, i.e., that Simula is somehow not "truly object-oriented." 

[...]
> AB>> I would argue that types are an old concept in object-oriented programming...
> EB>
> EB>Here you have me, sir. By not being more precise than I was, I have
> EB>left myself wide open. I could argue your point by citing a classic
> --------Deleted discussion on definition of typing------------------
> 
> I think you misunderstood me. I was not trying to be an obnoxious
> philosopher claiming that Smalltalk is typed in some sense.
> I agree that typing is a "new" topic with respect to Smalltalk.
> What I meant was simply that Simula is strongly typed (according to
> all reasonable definitions of strong typing (give me a break here)).
> and hence types are not a new concept in OOP.

You are right -- I did misunderstand you.

Further, when you said, "Strong typing and 'dynamic binding of method'
are theoretically _orthogonal_.", I read "orthogonal" (i.e., being
completely independent of each other), and thought "mutually
exclusive." I admit that upon a second reading, I saw my mistake.
While I will grant that some strong typing schemes may "get in the way
of dynamic binding," I will also state that strong typing and dynamic
binding are hardly mutually exclusive.

[...]
> 
> Ok good, but going back to the original topic again "evaluation of OOPLs",
> I don't think strong typing should be regarded as a discriminating feature of
> OOPLs. 

I fully agree. 

I think that I was not clear enough in the first part of my original
article. The intent was to to say that:

	- The criteria for judging whether a programming language is
	  object-oriented seem to vary widely, with few people (e.g.,
	  Wegner) taking the time to express their criteria in detail. 

	- For each candidate criterion there appear to be a number of
	  "exceptions." Specifically, given a criterion (e.g.,
	  classes), there is at least one "object-oriented programming
	  language" which "violates" the criterion (e.g., Self).

	- Many people fail to attach weights to each criterion, i.e.,
	  all criteria are equally important.

Thank you for the discussion.

				-- Ed Berard
				   (301) 353-9652