Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

fun main() {
    val numbers = (1..1_000_000).toList()

// Eager — creates two intermediate lists
    val eagerResult = numbers
        .filter  { it % 2 == 0 }
        .map     { it * it }
        .take(5)
    println("Eager:  $eagerResult")

// Lazy — no intermediate lists; stops after 5 elements found
    val lazyResult = numbers.asSequence()
        .filter  { it % 2 == 0 }
        .map     { it * it }
        .take(5)
        .toList()
    println("Lazy:   $lazyResult")

// generateSequence — infinite Fibonacci sequence
    val fibonacci: Sequence<Long> = generateSequence(Pair(0L, 1L)) {
        Pair(it.second, it.first + it.second)
    }.map { it.first }

println(fibonacci.take(10).toList())
    // [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

// sequence builder with yield
    val evens = sequence {
        var n = 0
        while (true) {
            yield(n)
            n += 2
        }
    }
    println(evens.take(6).toList())   // [0, 2, 4, 6, 8, 10]

// Sequence of file lines (hypothetical large file)
    val words = sequenceOf("the", "quick", "brown", "fox", "jumps")
    val result = words
        .filter { it.length >= 4 }
        .map    { it.replaceFirstChar { c -> c.uppercase() } }
        .toList()
    println(result)   // [Quick, Brown, Jumps]
}