6 ms·

Records and protocols meet your definition of OOP exactly.

didibus 8y ago
Well, like I said, we're in the realm of a semantic debate, and I'm definitly being pedantic. But, as I see it, records and types define only data. The former as an immutable map with pre-defined keys, the latter as a fixed set of data fields. Thus neither are an object. Protocols define only function signatures, without data. More like interfaces. Thus it too is not an object. Why am I being pedantic? Because data and functions are never coupled in this case. But in traditional OOP, an object groups data and methods, and are thus coupled together tightly.
- likeclockwork 8y ago
  But a record defines implementations of the protocol methods. Would you say Traits in rust aren't an OO construct? The data and methods are coupled in the record definition. The methods depend on having the records fields in scope.
  - didibus 8y ago
    > Would you say Traits in rust aren't an OO construct? I'd say traits in Rust, typeclasses in Haskell and Scala imlicit views are the equivalent to Clojure/Script protocols. And similarly, those constructs by themself aren't OOP. I think a simple proof is that if they were, then all OOP languages would have them. But because there are OOP languages (the most popular ones at that) which don't have them, then it follows this construct is not fundamental to OOP. > But a record defines implementations of the protocol methods. It's better to think of it as a protocol is extended to a type. It is not the record which defines the implementation. The methods don't belong to the record, they are independently defined, they can come from a dependency, they can even be shared with other types and other protocols. This is contrary to objects which define their own methods. > The data and methods are coupled in the record definition. Functions are associated with a protocol and a type independently of the record or protocol definition. This association is many to many. The same function can be associated over many protocols and many types. There is no coupling. You can even dissociate them. To add new associations or dissociate existing ones, you don't need to touch the record definition at all. > The methods depend on having the records fields in scope. They don't. Record fields aren't scoped to their associated methods. They are always public. There is no self or this scope. They are just normal functions like any other. You don't even need a protocol. Just write a function which takes a record and does something with it. Now if you want to make this function type polymorphic, you can use a protocol. I'm not sure I'm explaining myself very well. Think of an object. The object defines some data fields. And it defines some methods together. You can't use those methods with other objects. The ownership is tied to the object that defined them. The only way to share the methods is through inheritance. Similarly, you can only manipulate the data fields of an object through the object, because the object owns the access to them. Only if it chooses to make them public or expose a getter/setter are other objects allowed access. This is OOP. If you model your programs with objects like that, you are doing object oriented programming. Data is encapsulated behind objects, and can only be manipulated through sending a message (a method call) to the object. The object defines the set of possible methods for that data. You can't do that in Clojure/Script, because no object like construct exists that would allow you to do it. Now in Clojure/Script, you have datatypes. That is, data with an associated type. You can create custom ones, such as records. A record is a set of key/value pairs with an associated type. A Person record defines a type Person, with keys Age and Weight and their values. That's all a record does. It can't restrict access to its data, it can't expose methods, and it can't receive messages (method calls). You can now write functions that take input of this new type. Those functions can be defined anywhere. They have no special access to the data inside Person, there's no `this` or `self`. The functions don't live inside the datatype. Now, if you want a common set of functions to work over many different types, you can specify a protocol. That's all a protocol does. This is just functional programming. Sorry for the length. The distinctions are subtle, couldn't find a way to explain them with less words.
    - likeclockwork 8y ago
      > I'd say traits in Rust, typeclasses in Haskell and Scala imlicit views are the equivalent to Clojure/Script protocols. And similarly, those constructs by themself aren't OOP. I think a simple proof is that if they were, then all OOP languages would have them. But because there are OOP languages (the most popular ones at that) which don't have them, then it follows this construct is not fundamental to OOP. This seems completely circular to me. Your definition of OOP is really "whatever all OOP languages do"? > I'm not sure I'm explaining myself very well. Think of an object. The object defines some data fields. And it defines some methods together. You can't use those methods with other objects. The ownership is tied to the object that defined them. In Clojure you can't use a protocol method on a type that doesn't implement that protocol. I don't see it as being that different from D's Uniform Function Call Syntax (a free function can be called as a method of its first argument and vice versa.) What is OO to you? Is it Class Oriented Programming? Is it a programming paradigm or is it the list of features and practices common to a family of languages? Almost no common OO languages treat method calls as messages. It's just a function call with a (usually) hidden 'this' parameter. Applying a protocol function to a record that implements it isn't really any different, from a perspective of message passing. A message is passed to the record and based on its pedigree it decides how to respond. Plenty of OO languages don't have private data and allow direct access to object fields. Arguably, by your definition, it isn't OO at all to even provide for public fields. As long as the methods follow the data around or vice versa, in my view, encapsulation has been achieved. Enforcement is another concern, but it's not Jail Oriented Programming so I don't see that enforced encapsulation is a necessary condition for OO. A record implementing a protocol can receive method calls. All of its method implementations happen with the records own fields in scope (assuming you define them in the defrecord). It doesn't need to restrict access, if you'd like it to have private data.. respect its privacy and don't look. As I understand it, the state of the art in Class-Oriented Programming has been to define interfaces for everything, and then define classes that implement those interfaces, and then use the interface to type functions and methods. A Trait in Rust or a Protocol in Clojure just knocks out the middle man, the unnecessary and unwanted class. What's left is still OO, you can get rid of the class and all of it's baggage and still have plenty of OO left. > A record is a set of key/value pairs with an associated type. A Person record defines a type Person, with keys Age and Weight and their values. That's all a record does. It can't restrict access to its data, it can't expose methods, and it can't receive messages (method calls). You can now write functions that take input of this new type. Those functions can be defined anywhere. They have no special access to the data inside Person, there's no `this` or `self`. The functions don't live inside the datatype. Now, if you want a common set of functions to work over many different types, you can specify a protocol. That's all a protocol does. This is just functional programming. This, to me, is a description of object-oriented programming without the class ceremony. It's also functional programming. The use of records and protocols is functional programming, but the constructs themselves have OO nature. I don't think functional programming and object oriented programming are in opposition to each other. I think functional programming and mutable state heavy/class-happy programming don't mix but the latter is not my definition of OO.
- pjmlp 8y ago
  https://en.wikipedia.org/wiki/The_Art_of_the_Metaobject_Protocol https://en.wikipedia.org/wiki/The_Art_of_the_Metaobject_Prot... "In his 1997 talk at OOPSLA, Alan Kay called it "the best book anybody's written in ten years", and contended that it contained "some of the most profound insights, and the most practical insights about OOP", but was dismayed that it was written in a highly Lisp-centric and CLOS-specific fashion, calling it "a hard book for most people to read; if you don't know the Lisp culture, it's very hard to read"."
lorddoig 8y ago
Crucially they don't carry around mutable state by default. If you want a record with protocols to act like a stateful object you can do it, but you have to explicitly jump through hoops eg by embedding an atom in one of its fields and writing all your own getters/setters. It's not an especially pleasant or useful way to write Clojure(Script) but, as others have mentioned, it can be useful for things like achieving very high performance in certain situations.
- likeclockwork 8y ago
  Sure, they're immutable, but it's still very much OO. I've never heard of OO requiring mutable state.

Well, like I said, we're in the realm of a semantic debate, and I'm definitly being pedantic. But, as I see it, records and types define only data. The former as an immutable map with pre-defined keys, the latter as a fixed set of data fields. Thus neither are an object. Protocols define only function signatures, without data. More like interfaces. Thus it too is not an object. Why am I being pedantic? Because data and functions are never coupled in this case. But in traditional OOP, an object groups data and methods, and are thus coupled together tightly.

likeclockwork 8y ago
But a record defines implementations of the protocol methods. Would you say Traits in rust aren't an OO construct? The data and methods are coupled in the record definition. The methods depend on having the records fields in scope.
- didibus 8y ago
  > Would you say Traits in rust aren't an OO construct? I'd say traits in Rust, typeclasses in Haskell and Scala imlicit views are the equivalent to Clojure/Script protocols. And similarly, those constructs by themself aren't OOP. I think a simple proof is that if they were, then all OOP languages would have them. But because there are OOP languages (the most popular ones at that) which don't have them, then it follows this construct is not fundamental to OOP. > But a record defines implementations of the protocol methods. It's better to think of it as a protocol is extended to a type. It is not the record which defines the implementation. The methods don't belong to the record, they are independently defined, they can come from a dependency, they can even be shared with other types and other protocols. This is contrary to objects which define their own methods. > The data and methods are coupled in the record definition. Functions are associated with a protocol and a type independently of the record or protocol definition. This association is many to many. The same function can be associated over many protocols and many types. There is no coupling. You can even dissociate them. To add new associations or dissociate existing ones, you don't need to touch the record definition at all. > The methods depend on having the records fields in scope. They don't. Record fields aren't scoped to their associated methods. They are always public. There is no self or this scope. They are just normal functions like any other. You don't even need a protocol. Just write a function which takes a record and does something with it. Now if you want to make this function type polymorphic, you can use a protocol. I'm not sure I'm explaining myself very well. Think of an object. The object defines some data fields. And it defines some methods together. You can't use those methods with other objects. The ownership is tied to the object that defined them. The only way to share the methods is through inheritance. Similarly, you can only manipulate the data fields of an object through the object, because the object owns the access to them. Only if it chooses to make them public or expose a getter/setter are other objects allowed access. This is OOP. If you model your programs with objects like that, you are doing object oriented programming. Data is encapsulated behind objects, and can only be manipulated through sending a message (a method call) to the object. The object defines the set of possible methods for that data. You can't do that in Clojure/Script, because no object like construct exists that would allow you to do it. Now in Clojure/Script, you have datatypes. That is, data with an associated type. You can create custom ones, such as records. A record is a set of key/value pairs with an associated type. A Person record defines a type Person, with keys Age and Weight and their values. That's all a record does. It can't restrict access to its data, it can't expose methods, and it can't receive messages (method calls). You can now write functions that take input of this new type. Those functions can be defined anywhere. They have no special access to the data inside Person, there's no `this` or `self`. The functions don't live inside the datatype. Now, if you want a common set of functions to work over many different types, you can specify a protocol. That's all a protocol does. This is just functional programming. Sorry for the length. The distinctions are subtle, couldn't find a way to explain them with less words.
  - likeclockwork 8y ago
    > I'd say traits in Rust, typeclasses in Haskell and Scala imlicit views are the equivalent to Clojure/Script protocols. And similarly, those constructs by themself aren't OOP. I think a simple proof is that if they were, then all OOP languages would have them. But because there are OOP languages (the most popular ones at that) which don't have them, then it follows this construct is not fundamental to OOP. This seems completely circular to me. Your definition of OOP is really "whatever all OOP languages do"? > I'm not sure I'm explaining myself very well. Think of an object. The object defines some data fields. And it defines some methods together. You can't use those methods with other objects. The ownership is tied to the object that defined them. In Clojure you can't use a protocol method on a type that doesn't implement that protocol. I don't see it as being that different from D's Uniform Function Call Syntax (a free function can be called as a method of its first argument and vice versa.) What is OO to you? Is it Class Oriented Programming? Is it a programming paradigm or is it the list of features and practices common to a family of languages? Almost no common OO languages treat method calls as messages. It's just a function call with a (usually) hidden 'this' parameter. Applying a protocol function to a record that implements it isn't really any different, from a perspective of message passing. A message is passed to the record and based on its pedigree it decides how to respond. Plenty of OO languages don't have private data and allow direct access to object fields. Arguably, by your definition, it isn't OO at all to even provide for public fields. As long as the methods follow the data around or vice versa, in my view, encapsulation has been achieved. Enforcement is another concern, but it's not Jail Oriented Programming so I don't see that enforced encapsulation is a necessary condition for OO. A record implementing a protocol can receive method calls. All of its method implementations happen with the records own fields in scope (assuming you define them in the defrecord). It doesn't need to restrict access, if you'd like it to have private data.. respect its privacy and don't look. As I understand it, the state of the art in Class-Oriented Programming has been to define interfaces for everything, and then define classes that implement those interfaces, and then use the interface to type functions and methods. A Trait in Rust or a Protocol in Clojure just knocks out the middle man, the unnecessary and unwanted class. What's left is still OO, you can get rid of the class and all of it's baggage and still have plenty of OO left. > A record is a set of key/value pairs with an associated type. A Person record defines a type Person, with keys Age and Weight and their values. That's all a record does. It can't restrict access to its data, it can't expose methods, and it can't receive messages (method calls). You can now write functions that take input of this new type. Those functions can be defined anywhere. They have no special access to the data inside Person, there's no `this` or `self`. The functions don't live inside the datatype. Now, if you want a common set of functions to work over many different types, you can specify a protocol. That's all a protocol does. This is just functional programming. This, to me, is a description of object-oriented programming without the class ceremony. It's also functional programming. The use of records and protocols is functional programming, but the constructs themselves have OO nature. I don't think functional programming and object oriented programming are in opposition to each other. I think functional programming and mutable state heavy/class-happy programming don't mix but the latter is not my definition of OO.
pjmlp 8y ago
https://en.wikipedia.org/wiki/The_Art_of_the_Metaobject_Protocol https://en.wikipedia.org/wiki/The_Art_of_the_Metaobject_Prot... "In his 1997 talk at OOPSLA, Alan Kay called it "the best book anybody's written in ten years", and contended that it contained "some of the most profound insights, and the most practical insights about OOP", but was dismayed that it was written in a highly Lisp-centric and CLOS-specific fashion, calling it "a hard book for most people to read; if you don't know the Lisp culture, it's very hard to read"."

lorddoig 8y ago

Crucially they don't carry around mutable state by default. If you want a record with protocols to act like a stateful object you can do it, but you have to explicitly jump through hoops eg by embedding an atom in one of its fields and writing all your own getters/setters. It's not an especially pleasant or useful way to write Clojure(Script) but, as others have mentioned, it can be useful for things like achieving very high performance in certain situations.

likeclockwork 8y ago
Sure, they're immutable, but it's still very much OO. I've never heard of OO requiring mutable state.