A modern programming language that makes developers happier.

kotlinlang

How bad is it if `val` property doesn't always return the same value?  Say it has a getter, and does some computation on other mutable parts of the class. Is it horrible? Amazingly bad?

I would make this a function to make it clear to consumers that it’s calculated

But that might be Java habits bleeding through

yeah, that definitely seems like the smarter choice!

interestingly, Kotlin wont smart cast such fields... so there's no opportunity for null to sneak past

It's not bad, considering there's plenty of existing usage of non-constant `val` properties even in the Kotlin API itself, such as `List.size`.

I agree that it is not bad as long as it only changes when some property of the object changes, like `List.size`.  If it is something that is calculated randomly or has side effects, then being a `val` would be bad.

<https://kotlinlang.org/docs/reference/coding-conventions.html#functions-vs-properties>
&gt; Prefer a property over a function when the underlying algorithm:
&gt; • does not throw
&gt; • is cheap to calculate (or cached on the first run)
&gt; • returns the same result over invocations if the object state hasn't changed
so if it returns a different value without state changes, it's recommended not to use a `val`