using kotlin's lambda syntax instead of introducing a `fn` keyword

[Hongbo]

fn hello (...params) {
}
var lambda = fn (...params ) { ... }

kotlin alternatives:

let hello = {  (...params) => body}

There seems to be no ambiguity.

xs.map(fn (x) { x + 1 }) 

vs

xs.map({ (x)=> x + 1 })