[hackinthebochs]

First off, apologies for seemingly badgering you in various threads in this post. I don't usually look at usernames when replying so it was completely by accident.

>interactions between objects can be just as hard to understand as any other interactions.

While this is true, there are strictly fewer possible interactions compared to the same functionality written only using primitives. To put it simply, one must understand all code that has a bit of data in its scope to fully understand how that bit of data changes. The smaller the scopes your program operates in, the smaller the "interaction space", and the easier it is to reason about. Class hierarchies do add complexity, but its usually well contained. It adds to the startup cost of comprehending a codebase which is why people tend to hate it.

[gruseom]

That's hilarious. Well, you're welcome to "badger" (i.e., discuss) anytime. It's I who should apologize for producing every other damn comment in this thread.

In my experience, classes don't give the kind of scope protection you're talking about. They pretend to, but then you end up having to understand them anyway. True scope protection exists as (1) local variables inside functions, and (2) API calls between truly independent systems. (If the systems aren't truly independent, but just pretending to be, then you need to understand them anyway.)

[hackinthebochs]

You're right that the scope protection I'm talking about isn't as clear cut when it comes to classes. Design by contract is an attempt to address this. Client code can only refer to another object through a well-defined interface. Thus your limited scope is enforced by the type system itself. Furthermore, much of this discussion is about perception of complexity rather than actual complexity.

In python you can access any classes internals if you're persistent enough. However, the difficulty in doing so and the convention that says that's bad practice gives the perception of a separation, thus one does not need to be concerned about its implementation. It lowers the cognitive burden in using a piece of functionality.

Haven't you noticed this yourself? A simpler interface is much easier to use than a more complicated one. If you're familiar with python, perhaps you've used the library called requests, its a pythonic API for http reqeusts. Compare this to the core library API using urllib2. The mental load to perform the same action is about an order of magnitude smaller with requests than urllib2, and its because there are far more moving parts with the latter.

My contention is that if bits of data and code are exposed to you, it is essentially a part of the API, even if you never actually use it. You still must comprehend it on some level to ensure you're using data it can access correctly, aka interaction space (I feel like I'm selling a book here).