7 ms·

This is exactly what Object-Oriented programming was supposed to be. Passing messages to objects that know how to respond to them, without you needing to know h

This is exactly what Object-Oriented programming was supposed to be. Passing messages to objects that know how to respond to them, without you needing to know how they do it or them needing to know why you asked.

Aardwolf 14y ago
Isn't that exactly what calling a method of an interface does?
fmargaine 14y ago
Yep, this is basically how SmallTalk works: message passing.
jerf 14y ago
Yes, but it certainly was not what it became. I'm less impressed by one guy's stated goals forty years ago than what it actually became. That's not a criticism of Alan Kay. It's an observation that his saying a thing a long time ago didn't and doesn't change what actually was created, and what OO is today is not message passing. The very, very core of what we call OO today, the feature without which you can not call yourself OO, is the binding together of a structure with associated "methods" for operating on it into a single unit. It's a way of structuring programs (note I do not say "language"; C can be programmed in OO, for instance) that chooses the OO answer to the Expression Problem: http://c2.com/cgi/wiki?ExpressionProblem http://c2.com/cgi/wiki?ExpressionProblem There's other frippery... there's a LOT of other frippery, actually, tons and tons and tons... but that's the core. It is not message passing. And the attempt to map one to the other is pretty klunky and generally lossy in both directions, another sign they really aren't the same thing. Alan Kay's description of message passing, when read in English rather than Smalltalk, always sounded a lot more like Erlang than Smalltalk to me, but I observe that Smalltalk is what he in fact created as the manifestation of his ideas, not Erlang. I think we can't ignore that fact.
- gliese1337 14y ago
  No argument. My comment was meant more as a lament- "oh, Object Orientation, what you could have been!" - than as a claim that we don't need something else.
- seanmcdirmid 14y ago
  Yikes! The expression problem is a small deal and has been solved many different ways (I wrote a paper on this in 2001, I debated this point with Wadler in 2002, this is so old news). My favorite way today is to use traits and type members in Scala, but any language that supports open classes would be even more elegant. Also, its a non-issue in dynamically typed languages. We are only arguing pedantically about what OOP "means," and everyone has their own definition. Useless. My own definition associates OOP with object thinking, the deconstruction of your problem into interacting objects, and then the use of plumbing in your language that help you realize this deconstruction in a solution. What that plumbing is can vary greatly and involves some combination of methods, messaging, classes, interfaces traits, prototypes, constraints, behaviors, reactions, reflexes, patterns (beta style), state encapsulation, etc... I like the idea of MOP, its like focusing on one aspect of the plumbing and fixating around it; I could never write a program using messages alone in my domain (like I couldn't really write a compiler using actors!). MOP and OOP are not orthogonal, they are describe completely different granularity.
  - jerf 14y ago
    Yes, I know the expression problem is old news. So is OO. There are plenty of things coming out that move beyond it or beside it or incorporate it as a thing in the language rather than the thing the language is bent around, but that is still the core idea in OO. And if you carefully read my post again, you'll see I didn't give a definition. I talked about the one element that I've seen that is common across all of them. I can name OO languages with no first-class support for inheritance, no classes, no interfaces, or any of the other things you name, but I can not name an OO language that does not have some first-class binding of a structure to the methods to operate on it, nor can I show you an OO program in a non-OO language that is missing that, because that's essentially a logical contradiction. That's the single core idea that is what OO is. This dodges the "everybody has their own definition" problem entirely. Message passing as a primary means of structuring your program and OO are incompatible. One's going to have to be meshed within the other. One's this fundamentally asynchronous, distributed way of programming, and one is an elaboration on structured programming. Someone's on top. You get the same thing between FP and OO; you can put OO in FP or you can put FP in OO (quite popular, Python/Ruby/etc. fit here), but one is going to have to be on top. They can't be peers, they have fundamentally different ideas about what is most important.
- flyinRyan 14y ago
  >but I observe that Smalltalk is what he in fact created as the manifestation of his ideas Actually no. Dan Ingalls made Smalltalk-80, which is probably the one you know. Kay never liked ST-80, but I'm not convinced Kay ever had a clear vision of what OO should be, only what it shouldn't. He knows enough to say he doesn't like anything that's available but why hasn't he just made a manifestation of his ideas? It's much easier to deal with "no, not like that, like this" then someone who just constantly says "no, that's not it either". There were several previous versions of Smalltalk. Maybe he actually did make some of those. But they were dropped because they weren't powerful enough...
  - wnight 14y ago
    He has. This post https://news.ycombinator.com/item?id=4789877 https://news.ycombinator.com/item?id=4789877 has more details. But I think it was clear before this. Message-passing between non-shared state actors is a fundamentally different animal than "traditional" shared-state programing, whereas what is commonly thought of as OOP (special method-call syntax, class-based coding) is just sugar on any other language without changing the way things work under the hood. Certainly, using the word "object" was unfortunate because it distracted people whereas "message-passing" is more to the point, but if you see what it was supposed to achieve there really is only one thing it could mean.

Aardwolf 14y ago

Isn't that exactly what calling a method of an interface does?

fmargaine 14y ago

Yep, this is basically how SmallTalk works: message passing.

jerf 14y ago

Yes, but it certainly was not what it became. I'm less impressed by one guy's stated goals forty years ago than what it actually became. That's not a criticism of Alan Kay. It's an observation that his saying a thing a long time ago didn't and doesn't change what actually was created, and what OO is today is not message passing. The very, very core of what we call OO today, the feature without which you can not call yourself OO, is the binding together of a structure with associated "methods" for operating on it into a single unit. It's a way of structuring programs (note I do not say "language"; C can be programmed in OO, for instance) that chooses the OO answer to the Expression Problem: http://c2.com/cgi/wiki?ExpressionProblem http://c2.com/cgi/wiki?ExpressionProblem There's other frippery... there's a LOT of other frippery, actually, tons and tons and tons... but that's the core. It is not message passing. And the attempt to map one to the other is pretty klunky and generally lossy in both directions, another sign they really aren't the same thing. Alan Kay's description of message passing, when read in English rather than Smalltalk, always sounded a lot more like Erlang than Smalltalk to me, but I observe that Smalltalk is what he in fact created as the manifestation of his ideas, not Erlang. I think we can't ignore that fact.

gliese1337 14y ago
No argument. My comment was meant more as a lament- "oh, Object Orientation, what you could have been!" - than as a claim that we don't need something else.
seanmcdirmid 14y ago
Yikes! The expression problem is a small deal and has been solved many different ways (I wrote a paper on this in 2001, I debated this point with Wadler in 2002, this is so old news). My favorite way today is to use traits and type members in Scala, but any language that supports open classes would be even more elegant. Also, its a non-issue in dynamically typed languages. We are only arguing pedantically about what OOP "means," and everyone has their own definition. Useless. My own definition associates OOP with object thinking, the deconstruction of your problem into interacting objects, and then the use of plumbing in your language that help you realize this deconstruction in a solution. What that plumbing is can vary greatly and involves some combination of methods, messaging, classes, interfaces traits, prototypes, constraints, behaviors, reactions, reflexes, patterns (beta style), state encapsulation, etc... I like the idea of MOP, its like focusing on one aspect of the plumbing and fixating around it; I could never write a program using messages alone in my domain (like I couldn't really write a compiler using actors!). MOP and OOP are not orthogonal, they are describe completely different granularity.
- jerf 14y ago
  Yes, I know the expression problem is old news. So is OO. There are plenty of things coming out that move beyond it or beside it or incorporate it as a thing in the language rather than the thing the language is bent around, but that is still the core idea in OO. And if you carefully read my post again, you'll see I didn't give a definition. I talked about the one element that I've seen that is common across all of them. I can name OO languages with no first-class support for inheritance, no classes, no interfaces, or any of the other things you name, but I can not name an OO language that does not have some first-class binding of a structure to the methods to operate on it, nor can I show you an OO program in a non-OO language that is missing that, because that's essentially a logical contradiction. That's the single core idea that is what OO is. This dodges the "everybody has their own definition" problem entirely. Message passing as a primary means of structuring your program and OO are incompatible. One's going to have to be meshed within the other. One's this fundamentally asynchronous, distributed way of programming, and one is an elaboration on structured programming. Someone's on top. You get the same thing between FP and OO; you can put OO in FP or you can put FP in OO (quite popular, Python/Ruby/etc. fit here), but one is going to have to be on top. They can't be peers, they have fundamentally different ideas about what is most important.
flyinRyan 14y ago
>but I observe that Smalltalk is what he in fact created as the manifestation of his ideas Actually no. Dan Ingalls made Smalltalk-80, which is probably the one you know. Kay never liked ST-80, but I'm not convinced Kay ever had a clear vision of what OO should be, only what it shouldn't. He knows enough to say he doesn't like anything that's available but why hasn't he just made a manifestation of his ideas? It's much easier to deal with "no, not like that, like this" then someone who just constantly says "no, that's not it either". There were several previous versions of Smalltalk. Maybe he actually did make some of those. But they were dropped because they weren't powerful enough...
- wnight 14y ago
  He has. This post https://news.ycombinator.com/item?id=4789877 https://news.ycombinator.com/item?id=4789877 has more details. But I think it was clear before this. Message-passing between non-shared state actors is a fundamentally different animal than "traditional" shared-state programing, whereas what is commonly thought of as OOP (special method-call syntax, class-based coding) is just sugar on any other language without changing the way things work under the hood. Certainly, using the word "object" was unfortunate because it distracted people whereas "message-passing" is more to the point, but if you see what it was supposed to achieve there really is only one thing it could mean.