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The use of `class` for things that should be simple free functions

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Re: The use of `class` for things that should be simple free functions

#381

Post by cessor »

jimmaswell wrote: post #361
jl2718 wrote: post #360

Earlier quoted context omitted.

My first computer book was: “Data Structures + Algorithms = Programs”. Thinking in this way has simplified my code tremendously. I think OO is taught because it’s more tactile. Literally it takes more keystrokes, and so much is pattern repetition that it facilitates learning and feels like progress. Functional is like learning Latin by studying Ovid one word at a time. When books (or mips) were expensive, this was ho…

OO is just the most intuitive way to compartmentalize state to many people, me included.

I feel the same way.

Re: The use of `class` for things that should be simple free functions

#382

Post by taneq »

DonaldFisk wrote: post #353
taneq wrote: post #38

This reminds me of the blog rant "Execution in the Kingdom of Nouns": https://steve-yegge.blogspot.com/2006/03/execution-in-kingdo...

It's referred to in the article.

Believe it or not, that was added after my comment! (In an edit at 28/05/2020 14:30 - https://web.archive.org/web/20200528143032/https://quuxpluso... :)

Re: The use of `class` for things that should be simple free functions

#383

Post by wwright »

cessor wrote: post #380
savingGrace wrote: post #335

Earlier quoted context omitted.

I felt as though I should know the moral of the story, yet I did not. https://stackoverflow.com/a/11421598 Moral of the story is that closures and objects are ideas that are expressible in terms of each other, and none is more fundamental than the other. That's all there is to the statement under consideration.

True. But given that the difference in implementation appears to be arbitrary, the real differene between oop and fp must be evaluated in the domain of empirical research regarding their ergonomics. If one matches your natural thoughtpatterns more closely (be that abstract or concrete modelling) or educative efforts (it might be that one is easier to understand), or ease of implementation, that would be an argument f…

You absolutely do not need to understand lambda calculus to leverage FP. (And similarly, you don’t need to understand Turing machines to leverage imperative styles.)

Tools like ReactJS and regular expressions would indicate that the market for FP is quite large in spite of the popularity of Java as well, IMO

Re: The use of `class` for things that should be simple free functions

#384

Post by wwright »

gfxgirl wrote: post #362
savingGrace wrote: post #335

Earlier quoted context omitted.

I felt as though I should know the moral of the story, yet I did not. https://stackoverflow.com/a/11421598 Moral of the story is that closures and objects are ideas that are expressible in terms of each other, and none is more fundamental than the other. That's all there is to the statement under consideration.

Maybe I'm mis-understanding the definition of class or object but isn't a "File" in even Haskell an example of a class. Files have state which is either the read head or write head and in most languages you can change the head using seek. I don't think the fact that you call `file.seek` vs `seek(file)` the difference between functional and object oriented. functional people say "state = evil, side effects = evil" and…

I can’t speak for all functional programming advocates, but personally, when I criticize “classes” it is because of the overall design/culture and not because of encapsulating state/side effects.

- Subclassing is notoriously misleading and confusing and almost never truly useful (true subclassing, not abstract subclassing/interfaces).

- Class syntax/semantics are usually divorced from the other semantics of the language; closures are usually a much simpler design to achieve the same power. (You can get class-like ideas with simpler ideas too, but I think most “class” features don’t.)

- Culturally, classes are often viewed as mythic/special in a way that’s kind of out of touch with mapping problems to solutions. Look at “typical” Java code full of classes for crazy tasks like implementing 20 getters and constructing a factory to create callbacks. All of these things are related to the problem, but there’s a lot of friction/mismatch because people are taught to “use classes.”

Re: The use of `class` for things that should be simple free functions

#385

Post by wwright »

dataflow wrote: post #18

Counter-point: while in many situations this isn't the right approach, it's worth recognizing when this is the right approach, because they can look awfully similar. An example of this is graph searching, e.g. BFS or Dijkstra's algorithm. The typical implementation is a function. But if you make Dijkstra a class, with (say) a function to iterate through nodes, it lets you do several things that would be difficult wit…

IMO it’s even simpler to use a monad-type extension to functions to suspend state. (This can be coroutines/generators, explicit Haskell monads, some macros encapsulating longjmp or whatever.)

    queue
The monad-style extensions fits with the other pieces of the language much more naturally IMO. You could easily use a predicate monad to regain the functionality of the naive implementation, or a more complex monad if you want a complex BFS traversal, but the function looks almost identical either way.

Python and Ruby and Lua and JavaScript even do this! C++20 will probably make this somewhat more common too.

(The word “monad” may set off sirens here, but it really just refers to a feature similar to but somewhat more generic than “yield” in a coroutine/generator.)

Re: The use of `class` for things that should be simple free functions

#386

Post by dkersten »

munchbunny wrote: post #325
dkersten wrote: post #303

Earlier quoted context omitted.

> So instead of doing objects, you're doing closures that act like objects? No, I'm using using as-plain-as-possible data structures for my state, that I pass to functions that operate on it and return new state. Simple, composable, easy to test, easy to pass the state data elsewhere, serialize it or whatever else I might want to do. I'm not arguing against using classes or objects, but often its unnecessary and hidi…

Fair enough. I agree with you that: "Classes and objects have their place, but I feel they shouldn't always be the default choice, just because." Often the best things to do in an OOP language is to remember that you don't have to encapsulate everything, and sometimes it's just about bundling data/state. I may have highlighted the wrong point that I was responding to. I was making a point about the behavioral equival…

I agree with you. The only point in favour of using a closure that I want to point out (you already pointed out a big point in favour of objects: the dedicated and streamlined syntax) is that its a more a la carte way of doing objects: you choose how deep you want to go.

Of course in reality its not that bad because you can also use classes as much or little as you want and can use them simply for single dispatch, or namespacing, if you wish.

I do find that in practice syntax and features matter because they push you to think in a certain way and it can be hard to break away from that. For example, I write a lot of Clojure and really like functional languages, but when I use Java, Python or even C++, its all too easy to slip into the OOP mindset even when I set out to just "do functional" in those languages. Maybe that's my failing and its certainly not OOP's fault, but I think in practice (at least from observation) it seems most people are like this.

But yeah, I don't actually disagree with you on what you said.

Re: The use of `class` for things that should be simple free functions

#387

Post by AlexanderDhoore »

cessor wrote: post #379
AlexanderDhoore wrote: post #336

Earlier quoted context omitted.

It's code and state. Nothing more. Nothing less.

How do you model changes in state over time? (i.e. effects and processes?)

Is this a trick question? You mutate the state, of course.

Re: The use of `class` for things that should be simple free functions

#388

Post by [deleted] »

cessor wrote: post #378
AlexanderDhoore wrote: post #311

The venerable master Qc Na was walking with his student, Anton. Hoping to prompt the master into a discussion, Anton said "Master, I have heard that objects are a very good thing - is this true?" Qc Na looked pityingly at his student and replied, "Foolish pupil - objects are merely a poor man's closures." Chastised, Anton took his leave from his master and returned to his cell, intent on studying closures. He careful…

How much great learning the student could have done if he had not been insulted and physically abused by an impatient "educator".

[deleted]

Re: The use of `class` for things that should be simple free functions

#389

Post by JoeAltmaier »

Tomis02 wrote: post #365
JoeAltmaier wrote: post #198

Earlier quoted context omitted.

Sure, you can build your own object and pass the 'this' pointer around manually. You could use C for everything, and tediously do everything again that objects do for free. But why? There's a lot of object-hating going around. Its silly. Use objects to encapsulate functionality, they are good at that and everybody understands what it means.

> Use objects to encapsulate functionality Sadly objects are also used in an attempt to hide data (because direct access to data is considered dirty in OOP). Now, consider a non-trivial OOP class hierarchy. You have an object that needs to mutate another object's data (an object that is completely unrelated to your initial object). In order to solve this you have options: - completely rearchitect your code so that yo…

OR, don't use a 'setter', use a carefully named API that describes the purpose instead. Or design the two classes to share the data with locks. Or whatever your solution requires.

Yes breaking encapsulation willy-nilly is a bad thing. So don't.

I don't doubt there are bad programmers out there. Blaming the hammer for a bad carpenter is foolishness.

Btw objects are used for like 5 different things. Choose what works for your problem space.

Re: The use of `class` for things that should be simple free functions

#390

Post by zaphirplane »

twic wrote: post #42
makapuf wrote: post #3

Also known in python as "if your class has only two methods, one of which is init, it's a function" in the "stop writing classes" https://www.youtube.com/watch?v=o9pEzgHorH0 EDIT: typo, changed link

I have a few little classes that are clients for network services. They have a constructor which sets up an HTTP client or socket or something, and maybe prepares some metadata, and then a method to make a call to the service. I could write these clients as lambdas or nested functions which close over the stuff which init creates. But why? An object makes it much clearer that there is state.

I/O in constructor ? I thought that is an avoid
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