A question on Twitter : https://twitter.com/winterbe_/status/703162548300832768?lang=fr

How would you define them? Keep in mind that Int + Double should not work

Actually Int + Double does work

One reason would be that operators are dispatched statically, so there’s no need for them to be on Number at all

One can define maths operators for any type as extension methods

a coworker of mine has asked me if Kotlin has "higher kinded types", and I think the answer is "no", but I don't know enough about FP (and maybe Kotlin itself) to give him a proper response, including the possibility in the future for something like that to appear in Kotlin (and again, I think the answer is "no")

can anyone give me something I can tell him? (I want him to try Kotlin, and we're discussing it's pros and cons, basically)

@konsoletyper: I got better result with these codes below without lazy. I managed to update to kotlin 1.0 release version.

class Attachment(val name: String) {
    val isValidName = name.toLowerCase().endsWith(“.jpg”)
}

But not with this:

class Attachment(val name: String) {
    val isValidName by lazy { name.toLowerCase().endsWith(".jpg") }
}

@arcnor: it's a bit of a vague question. kotlin has something a bit better than Java generics, but it's not radically more powerful. your colleague probably means HKTs like in Scala, in which case the answer is no

Does Kotlin have facilities to make companion lazy objects?

I has many list items but I want the first item cached some value (resources from XML).

So I want write something like:

companion object {
        val inactiveColor by lazy { colorRes(R.color.asset_inactive) }
    }

Where colorRes() is a View-class extension function so it can’t be used in static context.

yes, I don’t see why this wouldn’t work

@yole: because I can’t call colorRes-function from static context.

@yole: I need an instance of View for that.

ah, missed that

@yole: but if I declare

inactiveColor

in scope of View instance, variable

inactiveColor

will be calculated in every view. But I want cache it as a some global value.

thanks @mikehearn

but it's a bit of a hard comparison. kotlin is not a direct subset of scala.

@egslava: you can have a static instance of

ApplicationContext

and from it retrieve your resources. And feel free to ask android-related questions in #C0B8M7BUY

@rafal: thanks simple smile But, is there more elegant solution?

@rafal, ok I understand, I could just rewrite delegatee.

(but I’m not sured)

I'm not sure what is not-elegant in this solution. What's more - you can create your own delegate e.q.

by lazyColor {resId}

@mikehearn: I know, but a lot of my colleagues have a strong FP background, so naturally they want to use FP when dealing with their languages, so I guess it's fair

sure

i wouldn't be against more powerful generics in kotlin myself. but there are higher priorities for quite a while, i think

yeah, like finishing JS support! (I'm waiting for that myself :D)

although I'm quite happy with the current status of Kotlin itself, so nothing to add for now