Comment by jph | Hacker News Reader

Comment by jph | Hacker News Reader

The author is accidentally promoting functional programming, without realizing it. He emphasizes "interoperable extensions" and "service abstractions" but what he's really describing are functional type signatures and interfaces.

His writes: "I now propose a candidate for the leverage provided by object-oriented service abstractions in design: The key design leverage provided by objects is the ability to define nontrivial abstractions that are modularly extensible, where instances of those extensions can interoperate in a first-class way." But he describes is not "object-oriented" in any sense of encapsulated data, internal state, and methods. Instead he describes the fold function, map function, and higher order functions.

The author touches on Alan Kay. Kay wrote this: "I'm sorry that I long ago coined the term "objects" for this topic because it gets many people to focus on the lesser idea. The big idea is "messaging" ... The Japanese have a small word -- ma -- for "that which is in between" -- perhaps the nearest English equivalent is "interstitial". The key in making great and growable systems is much more to design how its modules communicate rather than what their internal properties and behaviors should be."

Do you really believe the author of a paper explicitly about investigating the technical advantages of OO which also happens to touch on Haskell and ML is simply clueless about functional programming? And this ignoramus has somehow faked his way to the position of director of CMUs Software Engineering PhD program.

This seems like a stubbornly obtuse way to not engage in the paper's arguments.

Indeed; I have had the pleasure of having correspondence with Dr. Aldrich in the past. I had interest in implementing a static compiler for CMU's Plaid programming language, but found Go sufficient at the time. He also became involved with development of the Wyvern programming language. Nonetheless, he is well versed in programming language design and theory as that is his area of interest. It would be hard to imagine any related ignorance on his part.

Jonathan aldrich does come from the UW side of PL, which leans toward objects (a bias I share as well). But he knows his FP. Still, I'm not much for arguments by authority; either you see a proper comparison in the paper or not (I haven't looked closely enough). What both William and Jonathan both seem to miss, however, is more a discussion on object thinking, which I think would make the difference between OOP and fp more clear from a design perspective.

I don't think this is really an argument from authority since I'm not saying 'he's right because he has a PhD and teaches at a renowned university'. I'm saying that assuming he's ignorant of FP given both what he says in the paper and his background is silly and shallow.

It's not really fair to say that Aldrich 'misses' a discussion of object thinking, he just chooses to put the focus of that particular paper elsewhere - this is from the intro

Some of the advantages of object-oriented programming may be psychological in nature. For example, Schwill argues that “the object-oriented paradigm...is consistent with the natural way of human thinking” [28]. Such explanations may be important, but they are out of scope in this inquiry; I am instead in- terested in whether there might be significant technical advantages of object-oriented programming.

and

This success raises a natural question: Why has object-oriented programming been successful in practice?

Everyone reads these papers from different perspectives, so it's quite easy to say someone missed something (fair or not).

My criticism is that an analysis of OOP is incomplete if you avoid looking at...objects. It's like saying, we are going to ignore the objects themselves, and just focus on the technical features of the objects to see what the technical advantage of these features are. It is very reductionist...while objects favor a more holistic manner of thinking.

We probably (broadly) agree more than disagree. One reason FP/OOP comparisons are difficult is that FP is closely related to a mathematical formalism while OOP isn't and can't be. I think the tack he's taking is 'can we explain the popularity of OOP in terms of "technical" or really, "practical programming/software engineering" advantages'. It's a tricky needle eye to thread.

The objection 'that approach can't lead to useful insight' is a reasonable one but I don't think he's taking the approach out of ignorance or because he spaced out on something while typing it up - it's a deliberate choice, whatever its merits.

Ah, I never said he took this approach out of ignorance. I've talked about this with him before, and never found his arguments lacking.

It is nice that something is still going on in OOP.

Given the difference in both OOP and FP, I agree it certainly would be an interesting contrast to explore. Especially now, as FP is becoming more mainstream.

I really need to sit down and write that essay, but I always have better things to write and design essays are difficult to sell. A lot of the FP programming that goes on is just weak OOP with some immutability, closures, and list comprehensions. The real hardcore FP avoids not only mutation, but also aliases and identifiable objects. Object thinking is impossible in that context because nothing can have a name (beyond rolling your own GUIDs); it really is different.

> Do you really believe the author ... is simply clueless about functional programming?

I believe that his paper's descriptions of technical advantages of OO are not actually about OO, and instead are about FP and interfaces -- what he calls "service abstractions".

Notice this: when he describes ADTs, he glosses over their power; when he describes the evolution of object code, he glosses over the evolution of interfaces; when he describes messaging, he glosses over protocol endpoints.

IMHO his paper mostly glosses over all the actual technical advantages of OO vs. other approaches, namely OO state encapsulation, OO black boxing, OO inheritance, and OO composition.

He writes that the "key technical characteristic" of OOP is dynamic dispatch, and "is essential to supporting independent, interoperating extensions". OOP's key technical characteristic is not dynamic dispatch -- it's black boxing of data + state + methods. Moreover, dynamic dispatch is not essential to supporting extensions as he claims. To top it off, FP easily does dynamic dispatch by using higher level functions and type classes if you like.

you're making a fallacy of appeal to authority.

I'm not. I'm not saying anything about the quality of his argument, I'm talking about the stridently poor quality of your initial one which boils down to 'he doesn't know what he's talking about'. I think that's trivially and factually refutable.

I do think what he's trying to argue is both interesting and difficult and I'm not sure I'm entirely convinced by it. It doesn't merit 'he's clueless' and saying that does a disservice to both the paper and the discussion here.

Your later, concrete objections are actual objections but I don't feel I've understood the paper well enough to engage in them. I'd only say I'm also unsure whether they're really about what the paper is about. The fact that many, in fact most, programming formalisms and paradigms are largely isomorphic is both well-understood and rarely a source of practical insight, which is the stated goal of the paper.

[I guess this is now also a reply to a post that was heavily edited while I was replying to it]

Given the definition of 'object' used, things like modules, namespaces and first class functions can be (in some languages: are) objects

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