Eager comprehensions

A comprehension puts the produced value first, followed by one or more for clauses and optional if guards. Square brackets build an array; braces build a dictionary.

Clauses nest from left to right. Later equal dictionary keys replace the value without moving the key's original position.

fn main() {
  let squares = [x * x for x in 0..6 if x % 2 == 0]
  let parity = {x % 2: x for x in 0..5}
  println(squares)
  println(parity)
}