a = [0..100] and b = {"a":1, "b":2} are so simple and plain to use

There are factory methods:

val a = listOf(1,2,3,4)
val a1 = mutableList(1,2,3,4)
val a2 = (0..100).toList()

val b = mapOf("a" to 1, "b" to 2)
val b1 = mutableMapOf(....)

There are so many discussion about it and even KEEP proposal, please check it. It’s not even close so simple as you may think https://github.com/Kotlin/KEEP/pull/112

we can do a=[1,2] in C, Haskell, Python, and Javascript, the most languages support that, why not java/kotlin?

this KEEP seems good

No, it is not. It is full of problems

why those modern langauges features are so difficult to implent on java/kotlin?

What kind feature exactly?

the upside I said

there are many features

I use several langauges

Kotlin is not Python

Or

Kotlin is not LanguageX

but those things are not every special stuff, like macro in lisp, pattern matching in haskell, continuation in scheme

I’m not ready to discuss every particular feature and my opinion may not match Kotlin Team opinions, my point is simple: To implement any new feature in the language you need very good reason and a lot of pros that overweight cons. And if you have this reason and way to implement it, everyone may create KEEP proposal for Kotlin and discussed it with community and Kotlin Team

fine