The basic idea behind OOP is that data and behavior (upon that data) are inseparable and they are coupled by the idea of an object of a class. Object have data and methods that work with that (and other data). Obviously by the principles of OOP, objects that are just data (like C structs) are considered an anti-pattern. (...) This is clearly against the principal idea of OOP.

This is a tough question because it's based on quite a few faulty premises:

1. The idea that OOP is the only valid way to write code.
2. The idea that OOP is a well-defined concept. It's become such a buzzword that it's hard to find two people that can agree on what OOP is about.
3. The idea that OOP is about bundling data and behavior.
4. The idea that everything is/should be an abstraction.

I won't touch upon #1-3 much, because each could spawn their own answer, and it invites a lot of opinion-based discussion. But I find the idea of "OOP is about coupling data and behavior" to be especially troubling. Not only does it lead to #4, it also leads to the idea that everything should be a method. There's a difference between the operations that define a type, and the ways you can use that type. Being able to retrieve the ith element is essential to the concept of an array, but sorting is just one of the many things I can choose to do with one. Sorting doesn't need to be a method any more than "create a new array containing only the even elements" needs to be.

OOP is about using objects. Objects are just one way of achieving abstraction. Abstraction is a means to avoid unnecessary coupling in your code, not an end all unto itself. If your notion of a card is defined solely by the value of its suite and rank, it's fine to implement it as simple tuple or record. There's no non-essential details that any other part of the code could form a dependency on. Sometimes you just don't have anything to hide.

You wouldn't make isVisible a method of the Card type because being visible is likely not essential to your notion of a card (unless you have very special cards that can turn translucent or opaque...). Should it be a method of the Player type? Well, that's probably not a defining quality of players either. Should it be a part of some Viewport type? Well, that depends entirely on what you define a viewport to be and whether the notion of checking the visibility of cards is integral to defining a viewport.

It's very much possible isVisible should just be a free function.

The basic idea behind OOP is that data and behavior (upon that data) are inseparable and they are coupled by the idea of an object of a class. Object have data and methods that work with that (and other data). Obviously by the principles of OOP, objects that are just data (like C structs) are considered an anti-pattern. (...) This is clearly against the principal idea of OOP.

This is a tough question because it's based on quite a few faulty premises:

1. The idea that OOP is the only valid way to write code.
2. The idea that OOP is a well-defined concept. It's become such a buzzword that it's hard to find two people that can agree on what OOP is about.
3. The idea that OOP is about bundling data and behavior.
4. The idea that everything is/should be an abstraction.

I won't touch upon #1-3 much, because each could spawn their own answer, and it invites a lot of opinion-based discussion. But I find the idea of "OOP is about coupling data and behavior" to be especially troubling. Not only does it lead to #4, it also leads to the idea that everything should be a method. 

There's a difference between the operations that define a type, and the ways you can use that type. Being able to retrieve the ith element is essential to the concept of an array, but sorting is just one of the many things I can choose to do with one. Sorting doesn't need to be a method any more than "create a new array containing only the even elements" needs to be.

OOP is about using objects. Objects are just one way of achieving abstraction. Abstraction is a means to avoid unnecessary coupling in your code, not an end all unto itself. If your notion of a card is defined solely by the value of its suite and rank, it's fine to implement it as simple tuple or record. There's no non-essential details that any other part of the code could form a dependency on. Sometimes you just don't have anything to hide.

You wouldn't make isVisible a method of the Card type because being visible is likely not essential to your notion of a card (unless you have very special cards that can turn translucent or opaque...). Should it be a method of the Player type? Well, that's probably not a defining quality of players either. Should it be a part of some Viewport type? Once again that depends on what you define a viewport to be and whether the notion of checking the visibility of cards is integral to defining a viewport.

It's very much possible isVisible should just be a free function.

The basic idea behind OOP is that data and behavior (upon that data) are inseparable and they are coupled by the idea of an object of a class. Object have data and methods that work with that (and other data). Obviously by the principles of OOP, objects that are just data (like C structs) are considered an anti-pattern. (...) This is clearly against the principal idea of OOP.

This is a tough question because it's based on quite a few faulty premises:

1. The idea that OOP is the only valid way to write code.
2. The idea that OOP is a well-defined concept. It's become such a buzzword that it's hard to find two people that can agree on what OOP is about.
3. The idea that OOP is about bundling data and behavior.
4. The idea that everything is/should be an abstraction.

I won't touch upon #1-3 much, because each could spawn their own answer, and it invites a lot of opinion-based discussion. But I find the idea of "OOP is about coupling data and behavior" to be especially troubling. Not only does it lead to #4, it also leads to the idea that everything should be a method. There's a difference between the operations that define a type, and the ways you can use that type. Being able to retrieve the ith element is essential to the concept of an array, but sorting is just one of the many things I can choose to do with one. Sorting doesn't need to be a method any more than "create a new array containing only the even elements" needs to be.

OOP is about using objects. Objects are just one way of achieving abstraction. Abstraction is a means to avoid unnecessary coupling in your code, not an end all unto itself. If your notion of a card is defined solely by the value of its suite and rank, it's fine to implement it as simple tuple or record. There's no non-essential details that any other part of the code could form a dependency on. Sometimes you just don't have anything to hide.

The basic idea behind OOP is that data and behavior (upon that data) are inseparable and they are coupled by the idea of an object of a class. Object have data and methods that work with that (and other data). Obviously by the principles of OOP, objects that are just data (like C structs) are considered an anti-pattern. (...) This is clearly against the principal idea of OOP.

This is a tough question because it's based on quite a few faulty premises:

1. The idea that OOP is the only valid way to write code.
2. The idea that OOP is a well-defined concept. It's become such a buzzword that it's hard to find two people that can agree on what OOP is about.
3. The idea that OOP is about bundling data and behavior.
4. The idea that everything is/should be an abstraction.

I won't touch upon #1-3 much, because each could spawn their own answer, and it invites a lot of opinion-based discussion. But I find the idea of "OOP is about coupling data and behavior" to be especially troubling. Not only does it lead to #4, it also leads to the idea that everything should be a method. There's a difference between the operations that define a type, and the ways you can use that type. Being able to retrieve the ith element is essential to the concept of an array, but sorting is just one of the many things I can choose to do with one. Sorting doesn't need to be a method any more than "create a new array containing only the even elements" needs to be.

OOP is about using objects. Objects are just one way of achieving abstraction. Abstraction is a means to avoid unnecessary coupling in your code, not an end all unto itself. If your notion of a card is defined solely by the value of its suite and rank, it's fine to implement it as simple tuple or record. There's no non-essential details that any other part of the code could form a dependency on. Sometimes you just don't have anything to hide.

You wouldn't make isVisible a method of the Card type because being visible is likely not essential to your notion of a card (unless you have very special cards that can turn translucent or opaque...). Should it be a method of the Player type? Well, that's probably not a defining quality of players either. Should it be a part of some Viewport type? Well, that depends entirely on what you define a viewport to be and whether the notion of checking the visibility of cards is integral to defining a viewport.

It's very much possible isVisible should just be a free function.