JuniorTheoryCommon

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

KOTLIN

fun <T> firstOr(items: List<T>, fallback: T): T {
    return if (items.isEmpty()) fallback else items[0]
}

fun main() {
    println(firstOr(listOf("x", "y"), "none"))
    println(firstOr(emptyList<Int>(), 0))
}

x 0

Expecting a compile error because the calls use different types: T belongs to one call, so the same function works with String and then with Int.
Expecting T to be written at every call: Kotlin infers it from the arguments, the same way listOf works out the type of its elements.

What does firstOr(emptyList<String>(), "none") print?
Why is List<String> also an example of a generic type?

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JuniorTheoryCommon

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

KOTLIN

fun <T> firstOr(items: List<T>, fallback: T): T {
    return if (items.isEmpty()) fallback else items[0]
}

fun main() {
    println(firstOr(listOf("x", "y"), "none"))
    println(firstOr(emptyList<Int>(), 0))
}

x 0

Expecting a compile error because the calls use different types: T belongs to one call, so the same function works with String and then with Int.
Expecting T to be written at every call: Kotlin infers it from the arguments, the same way listOf works out the type of its elements.

What does firstOr(emptyList<String>(), "none") print?
Why is List<String> also an example of a generic type?

Back to questions Open topic in roadmap →Answer it yourself — Quiz