Joe Armstrong: "I think the lack of reusability comes in object-oriented languages, not in functional languages. Because the problem with object-oriented languages is they've got all this implicit environment that they carry around with them. You wanted a banana but what you got was a gorilla holding the banana and the entire jungle. If you have referentially transparent code, if you have pure functions-all the data comes in its input arguments and everything goes out and leaves no state behind-it's incredibly reusable. You can just reuse it here, there, and everywhere. When you want to use it in a different project, you just cut and paste this code into your new project. Programmers have been conned into using all these different programming languages and they've been conned into not using easy ways to connect programs together. The Unix pipe mechanism-A pipe B pipe C-is trivially easy to connect things together. Is that how programmers connect things together? No. They use APIs and they link them into the same memory space, which is appallingly difficult and isn't cross-language. If the language is in the same family it's OK-if they're imperative languages, that's fine. But suppose one is Prolog and the other is C. They have a completely different view of the world, how you handle memory. So you can't just link them together like that. You can't reuse things. There must be big commercial interests for whom it is very desirable that stuff won't work together."
- Peter Seibel, Coders at Work: Reflections on the Craft of Programming
Something else I want to mention: what's written above will most likely result in some sort of warmed up discussion in regards to object oriented programming versus something else. Or inheritance versus strategies. Or virtual methods versus method passing. Or whatever else hackernews finds worthy of a discussion this time around.
All of that is entirely irrelevant to the point I'm making which is that monolithic pieces of code are a bad idea. And our solution to monolithic code in Python are classes. If your hammer of choice is Haskell then use whatever the equivalent in Haskell looks like. Just don't force me to fork your library because you decided a layered API is not something you want to expose to your user.
Aha! Good point. TL;DR! Only skimmed, as others have commented, it was far too long. Perhaps the title should have been Python rant: Write More Classes!. The point is, the themes touched upon in the article are greater. The author's wish not to raise them is .. hereby noted, but not understood, really, when appealing to a larger audience. You can't have it both ways.
1. When OO was on the brink of becoming mainstream, let's say early 90's, there was an awful lot of the most idiotic rubbish talked about reusability. For example I recall one magazine article that, with a completely straight face, told readers that you would be able to buy an "Aeroplane" class that you could slot into pretty much any application that dealt with aeroplanes. So Joe has a point here.
2. This is not an argument for not using classes within a single codebase. And indeed when I see Erlang functions pushing all the relevant state around as parameters in a big mess of tuples and lists like a crazy baglady with all her possessions in a shopping cart, the benefits of encapsulating it all become clear.
I'm not aware of Joe Armstrong having extensive OO experience - either as a programmer or a language designer. Could you fill me in? Perhaps the picture I have is completely wrong. Erlang is from 1986. Did he gather extensive OO experience before? In Smalltalk? Or on the side while developing Erlang?
According to a message he posted[0] on the erlang-questions mailing list, since 1967 he has written in Fortran, Lisp, Prolog, Smalltalk, Erlang, C, C++, Java, Python, Ruby, Lua, Javascript, Haskell, ML and OCaml.
I italicised all the object-oriented ones. Saying that Joe Armstrong doesn't have "extensive OO experience" is pretty comical!
About C++: "I saw C++ coming and read the book - or at least tried to read the book - there's a dent in the wall behind my piano, where the book hit the wall"
About Smalltalk: "I learnt (with various degrees of proficiency) [...] smalltalk [...] and became proficient in Prolog (aggghhh - the beauty ....)"
About the others: " I also (later) tried Python (ok), Ruby (ok)".
We might vary in our perception, but I would not call this extensive experience, "trying" some languages and "trying" to read a book.
I would call "I've written some systems in Java for 10 years" extensive Java experience.
If you read what he wrote (not just this quote), it is clear that he has a better grasp of OO than most OO practitioners and language designers.
And especially since OO is not well defined (see pg's quote of Jon Rees' characterization), most OO people can, and often do, claim everyone who uses a different OO definition than they do has no experience.
The quote posted in the initial comment really has no relevance to Armin's article so it's fair enough to call it out in this context.
To attack the quote itself by simply assuming the author is inexperienced in OO just silly. Particularly so, given that Joe Armstrong has a grasp of computer languages that most of us could only ever dream of.
I stand to this quote, Joe Armstrong has no documented OO experience (OO development for some years, development of an OO language etc.) and is quoted as an expert on the topic of classes. None of the people who have voted down all my comments have shown any experience in OO/classes development of Joe Armstrong. Joe Armstrong admitted to bash OO in a blog post ("silly" see quote above) to stir up people.
[Edit] It's the same when people quote Linus on GUIs. He might be an excellent kernel hacker, with a great understanding of large scale open source development, but his opinion on GUI is as good as everyone else. Or how people quote Wozniak on everything. This is not science but a guru cult. I'm proposing that we move our industry to facts and experiments and end the pop culture and guru cults. I'm not with Raganwald that we should embrace this pop culture. This is the reason that I vehemently disagree when people cite Joe Armstrong as an expert on classes or when Joe Armstrong tries to stir up people my bashing OO.
(as a side note, your argument does not make logical sense. Designing A does not make me an expert in B.)
I do not "insist" that he is a "dilettante", I question people on this thread quoting him as an expert on OO as there without showing that he is an expert on OO. Beside I give circumstantial evidence why he isn't ("Tried Java ...", "Threw C++ book at the wall ..."). I think it's important to differentiate strong opinion from expert.
And there are more indications: His understanding of "isolation" in the quoted text above is very influenced by him being the Erlang creator and the way Erlang thinks of isolation (processes). None of the (C++/Java/Ruby) OO programmers I know would use "isolation" in an OO context that sense (one error crashing other programs in the same VM).
Several people in HN should know more about OO than Armstrong.
There are academics that have taught and worked for decades on OO systems and concepts among the crowd, unlike Joe.
In general, popular language creators are hardly the more knowledgable of the various PL concepts and issues. Simon Peyton Jones probably knows hundred times more about such stuff than Matz or Guido do, for example.
It's worth pointing out that the original comment claimed Armstrong had no OO experience... not simply that Armstrong wasn't the most knowledgable OO programmer on HN.
OCaml, as the name ("Objective Caml") implies, also supports object-oriented programming. It actually has a pretty clever implementation of it as well. That said, many people tend to stick to the functional bits of OCaml and don't venture out into the OOP bits very often.
I thought about italicising OCaml as well, but I'd hesitate to call it an object-oriented language. It's more like a functional language that happens to have an object system.
Likewise Common Lisp has an object system (CLOS) but I wouldn't call it an object-oriented language.
" Is Erlang object oriented?
Joe Armstrong: Smalltalk got a lot of the things right. So if your question is about what I think about object oriented programming, I sort of changed my mind over that. I wrote a an article, a blog thing, years ago - Why object oriented programming is silly. I mainly wanted to provoke people with it. They had a quite interesting response to that and I managed to annoy a lot of people, which was part of the intention actually. I started wondering about what object oriented programming was and I thought Erlang wasn't object oriented, it was a functional programming language.
Then, my thesis supervisor said "But you're wrong, Erlang is extremely object oriented". He said object oriented languages aren't object oriented. I might think, though I'm not quite sure if I believe this or not, but Erlang might be the only object oriented language because the 3 tenets of object oriented programming are that it's based on message passing, that you have isolation between objects and have polymorphism.
Alan Kay himself wrote this famous thing and said "The notion of object oriented programming is completely misunderstood. It's not about objects and classes, it's all about messages". He wrote that and he said that the initial reaction to object oriented programming was to overemphasize the classes and methods and under emphasize the messages and if we talk much more about messages then it would be a lot nicer. The original Smalltalk was always talking about objects and you sent messages to them and they responded by sending messages back.
But you don't really do that and you don't really have isolation which is one of the problems. Dan Ingalls said yesterday (I thought it was very nice) about messaging that once you got messaging, you don't have to care where the message came from. You don't really have to care, the runtime system has to organize the delivery of the message, we don't have to care about how it's processed. It sort of decouples the sender and the receiver in this kind of mutual way. That's why I love messaging.
The 3 things that object oriented programming has it's messaging, which is possibly the most important thing. The next thing is isolation and that's what I talked about earlier, that my program shouldn't crash your program, if the 2 things are isolated, then any mistakes I make in my program will not crash your program. This is certainly not true with Java. You cannot take 2 Java applications, bung them in the JVM and one of them still halts the machine and the other one will halt as well. You can crash somebody else's application, so they are not isolated.
The third thing you want is polymorphism. Polymorphism is especially regarding messaging, that's just there for the programmer's convenience. It's very nice to have for all objects or all processes or whatever you call them, to have a printMe method - "Go print yourself" and then they print themselves. That's because the programmers, if they all got different names, the programmer is never going to remember this, so it's a polymorphism. It just means "OK, all objects have a printMe method. All objects have a what's your size method or introspection method."
Erlang has got all these things. It's got isolation, it's got polymorphism and it's got pure messaging. From that point of view, we might say it's the only object oriented language and perhaps I was a bit premature in saying that object oriented languages are about. You can try it and see it for yourself."
It depends a lot on how one defines OO, but in this regard he has -- or at least he has given some thought for it.
The answer to this question is supposed to be in "The Early History of Smalkalk", though I haven't re-read it.
Anyway, I just asked on the Fonc mailing list, and got an incredibly detailed answer from Alan Kay himself. To sum it up, someone asked him what he was doing, and he didn't quite have a name for that yet. Heck, he was at the stage of narrowing it down mathematically. So he just answered "object oriented programming", because it fitted with the vocabulary of the time, and went back to work.
He did later regretted this label.
Now, it's not even sure a better terminology would have helped much. Alan Kay reckons that "it might have helped to have better terminology", but it would probably have been hijacked too:
> The success of the ideas made what we were doing popular, and people wanted to be a part of it. This led to using the term "object oriented" as a designer jeans label for pretty much anything (there was even an "object-oriented" COBOL!). This appropriation of labels without content is a typical pop culture "fantasy football" syndrome.
Because "communicating with messages" is one of the important features of objects, but objects are the focus.
The confusion, I think, mostly came about because in the late 1980s early 1990s, an explosion of "Object-oriented" programming happend by gluing classes into existing popular structured programming languages -- producing ObjectPascal and C++ which became the popular "OO" languages which became what "OO" meant to lots of people (Objective-C was a contemporary, and despite being C-based like C++ was more like Kay's idea of OO than C++, but didn't become popular until later.)
So what became popularly conflated with "object oriented" programming was statically-typed, class-oriented programming typified by C++ and similar languages (e.g., Java.)
There are certainly ways (often not the same ways between languages) in which newer languages -- Erlang, Python/Ruby, etc. -- are more "object oriented" than Java/C++-style languages.
being googleable and knowing what he is talking about doesnt mean that his this quote is relavant in this context. What he said is a good piece of advice, but only when looked through larger window of programming. When we are talking about only python and choices of coding style in python, his quote looks like santa on valentines day!
Ya he doesnt. I think the person who brought him into discussion out of context deserves this. As I said being a santa is not bad, but someone who brought santa on valentines day is wrong
Joe Armstrong: "I think the lack of reusability comes in object-oriented languages, not in functional languages. Because the problem with object-oriented languages is they've got all this implicit environment that they carry around with them. You wanted a banana but what you got was a gorilla holding the banana and the entire jungle. If you have referentially transparent code, if you have pure functions-all the data comes in its input arguments and everything goes out and leaves no state behind-it's incredibly reusable. You can just reuse it here, there, and everywhere. When you want to use it in a different project, you just cut and paste this code into your new project. Programmers have been conned into using all these different programming languages and they've been conned into not using easy ways to connect programs together. The Unix pipe mechanism-A pipe B pipe C-is trivially easy to connect things together. Is that how programmers connect things together? No. They use APIs and they link them into the same memory space, which is appallingly difficult and isn't cross-language. If the language is in the same family it's OK-if they're imperative languages, that's fine. But suppose one is Prolog and the other is C. They have a completely different view of the world, how you handle memory. So you can't just link them together like that. You can't reuse things. There must be big commercial interests for whom it is very desirable that stuff won't work together."
- Peter Seibel, Coders at Work: Reflections on the Craft of Programming