JuniorTheoryCommon

What does the program print (lines separated by spaces)?

KOTLIN

fun main() {
    val a = mutableListOf(1).apply { add(2) }
    val b = mutableListOf(1).let { it.add(2) }
    println(a)
    println(b)
}

[1, 2] true

Expecting [1, 2] [1, 2]: thinking let returns the list. let returns the lambda's last value, and add returns true.
Expecting true for a: thinking apply returns what its lambda computes. apply always returns the object itself, here the list [1, 2].

JuniorTheoryCommon

KOTLIN

fun main() {
    val a = mutableListOf(1).apply { add(2) }
    val b = mutableListOf(1).let { it.add(2) }
    println(a)
    println(b)
}

[1, 2] true

Expecting [1, 2] [1, 2]: thinking let returns the list. let returns the lambda's last value, and add returns true.
Expecting true for a: thinking apply returns what its lambda computes. apply always returns the object itself, here the list [1, 2].