10. Ranges & Progressions

Ranges describe a sequence of values with a start and an end. They power for loops, membership checks, and more.

fun main() {
    // closed range: 1, 2, ..., 5
    println((1..5).joinToString())

    // half-open range with until: stops before 5
    println((1 until 5).joinToString())

    // counting down
    println((10 downTo 1).joinToString())

    // a step changes the increment
    println((0..10 step 2).joinToString())

    // membership test
    val x = 7
    println("$x in 1..10 -> ${x in 1..10}")

    // ranges also work on Char
    println(('a'..'e').joinToString(""))
}

Running it:

$ kotlin run
1, 2, 3, 4, 5
1, 2, 3, 4
10, 9, 8, 7, 6, 5, 4, 3, 2, 1
0, 2, 4, 6, 8, 10
7 in 1..10 -> true
abcde

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