Something like this? (I haven't tested it) ``` fun...

# announcements

[Ruckus]

Something like this? (I haven't tested it)

fun <T> MutableList<T>.upsert(source: List<T>, predicate: (existing: T, new: T) -> Boolean) {
    for (item in source) {
        val index = indexOfFirst { predicate(it, item) }
        if (index >= 0) set(index, item) else add(item)
    }
}

(Note that it's adding to the list while still using it. You may want to save new items to a separate list and add them all at the end after processing.)

[adam-mcneilly]

I think predicate(it, item) is a bug.

[adam-mcneilly]

Or did you intend to call it with the same parameter twice? In that line, it and item are equivalent aren't they?

[Ruckus]

No, it is coming from indexOfFirst which is called on `this, and item is coming from source

[adam-mcneilly]

Ohhh gotcha

[adam-mcneilly]

derp sorry

[paulex]

I will test this when I get home