This is the stdlib implementation of MutableMap.ge...

# announcements

[Nir]

This is the stdlib implementation of MutableMap.getOrPut

public inline fun <K, V> MutableMap<K, V>.getOrPut(key: K, defaultValue: () -> V): V {
    val value = get(key)
    return if (value == null) {
        val answer = defaultValue()
        put(key, answer)
        answer
    } else {
        value
    }
}

It seems like either the implementation or the description is wrong:

Returns the value for the given key. If the key is not found in the map, calls the defaultValue function, puts its result into the map under the given key and returns it.

println(mutableMapOf<Int, Int?>(5 to null).getOrPut(5) { 10 })

Prints 10. However, 5 is "in the map" (println(5 in mutableMapOf<Int, Int?>(5 to null) prints true).
kotlin nulls are very tricky in generic code.

[Marc Knaup]

https://youtrack.jetbrains.com/issue/KT-21392

[Nir]

@Marc Knaup bingo, thank you

[Nir]

FWIW I totally agree with what you wrote, I dislike the comment on that thread that amounts to "not my use case"

[Nir]

It's also a shame that it's one lookup

[Nir]

I mean, two