Summary - Collection stdlib

Combine windowed, chunked and zip to write a data pipeline.

Summary - Collections stdlib

In this group you saw advanced collections stdlib methods: sliding windows with windowed, splitting with chunked, merging/splitting with zip/unzip, running accumulation with scan, and flattening with flatMap/flatten.

This lesson includes a small task that combines three of them: you will split a list with chunked and sum each chunk with sum. This pattern brings together the power of the collections stdlib.

Exercise Summary: chunk sums with chunked

In main assign the result of listOf(1, 2, 3, 4, 5, 6).chunked(3) { it.sum() } to a variable and print it with println.

Show example solution

fun main() {
    val sums = listOf(1, 2, 3, 4, 5, 6).chunked(3) { it.sum() }
    println(sums)
}

Test yourself

Which method shows running intermediate results in a list?
- reduce
- fold
- scan
- forEach
Show answer

scan — scan collects each intermediate result in a list.
Match the stdlib methods

windowed(2)

Sliding window
chunked(2)

Consecutive chunk
zip(other)

Parallel merge
flatMap { }

Transform and flatten

Complete the chunked call

val sums = listOf(1, 2, 3, 4).____(2) { it.sum() }

Show answer

val sums = listOf(1, 2, 3, 4).chunked(2) { it.sum() }

Next lesson: KClass

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