What exactly is happening with the `.count` lambda...

# getting-started

[scottiedog45]

What exactly is happening with the .count lambda inside this function; it looks to me like a lambda is being passed to an Int? What?

fun bingo(ticket: Array<Pair<String, Int>>, win: Int) =
    if (ticket.count { it.second.toChar() in it.first } >= win) "Winner!" else "Loser!"

I’m on https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/count.html and don’t see anything like a closure happening for Array.count

[Al Warren]

Given the definition

inline fun <T> Array<out T>.count(
    predicate: (T) -> Boolean
): Int

Note that predicate: (T) -> Boolean is a lambda.

The example leaves out the parenthesis and could be rewritten like this:

if (
    ticket.count ( 
        { it.second.toChar() in it.first } 
    ) >= win
) "Winner!"
else "Loser!"

In other words, count the number of results produced by the predicate it.second.toChar() in it.first.

[scottiedog45]

Thanks @Al Warren!