Scala downwards or decreasing for loop?

Question

In Scala, you often use an iterator to do a for loop in an increasing order like:

for(i <- 1 to 10){ code }

How would you d

Answer 1

You can use Range class:

val r1 = new Range(10, 0, -1)
for {
  i <- r1
} println(i)

Answer 2

for (i <- 10 to (0,-1))

The loop will execute till the value == 0, decremented each time by -1.

Answer 3

scala> 10 to 1 by -1
res1: scala.collection.immutable.Range = Range(10, 9, 8, 7, 6, 5, 4, 3, 2, 1)

Answer 4

You can use : for (i <- 0 to 10 reverse) println(i)

Answer 5

The answer from @Randall is good as gold, but for sake of completion I wanted to add a couple of variations:

scala> for (i <- (1 to 10).reverse) {code} //Will count in reverse.

scala> for (i <- 10 to(1,-1)) {code} //Same as with "by", just uglier.

Answer 6

Having programmed in Pascal, I find this definition nice to use:

implicit class RichInt(val value: Int) extends AnyVal {
  def downto (n: Int) = value to n by -1
  def downtil (n: Int) = value until n by -1
}

Used this way:

for (i <- 10 downto 0) println(i)