Increment for-loop by 2 in Scala

Try for (a <- 0 until max by 2)

Note the difference between to and until. With a strict i < max you will want until.

val max = 10

scala> for(i <- 0 until max by 2)
     | println(i)
0
2
4
6
8

scala> for(i <- 0 to max by 2)
     | println(i)
0
2
4
6
8
10