A function type can take zero, one, or several parameters.
Things start to get a bit complicated from a generics standpoint. Use
a comma-delimited list of types to declare the types used by the
function (e.g., <K, V, T>).
Here, collectify() converts a Map into a List, iterating over the
map pairs and using a supplied transform function type to convert the
pair into a single value for the list.
You can learn more about this in:
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fun <K, V, T> collectify(input: Map<K, V>, transform: (K, V) -> T): List<T> {2
val result = mutableListOf<T>()3
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for ((key, value) in input) { result.add(transform(key, value)) }5
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return result.toList()7
}8
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fun main() {10
val stuff = mapOf("foo" to "bar", "goo" to "baz")11
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println(stuff)13
println(collectify(stuff) { key, value -> "${key.toUpperCase()}: ${value.toUpperCase()}" } )14
}