buildSequence

fun <T> buildSequence(
    builderAction: suspend SequenceBuilder<T>.() -> Unit
): Sequence<T>
(source)

Platform and version requirements: Kotlin 1.1

Builds a Sequence lazily yielding values one by one.

import kotlin.test.*
import kotlin.coroutines.experimental.buildIterator
import kotlin.coroutines.experimental.buildSequence

fun main(args: Array<String>) {
//sampleStart
val sequence = buildSequence {
    val start = 0
    // yielding a single value
    yield(start)
    // yielding an iterable
    yieldAll(1..5 step 2)
    // yielding an infinite sequence
    yieldAll(generateSequence(8) { it * 3 })
}

println(sequence.take(7).toList()) // [0, 1, 3, 5, 8, 24, 72]
//sampleEnd
}
import kotlin.test.*
import kotlin.coroutines.experimental.buildIterator
import kotlin.coroutines.experimental.buildSequence

fun main(args: Array<String>) {
//sampleStart
fun fibonacci() = buildSequence {
    var terms = Pair(0, 1)

    // this sequence is infinite
    while(true) {
        yield(terms.first)
        terms = Pair(terms.second, terms.first + terms.second)
    }
}

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

See Also

kotlin.sequences.generateSequence