I'm trying to understand the signature of flapMap that allows it to "strip
down" Optional from a type, when called on an Optional collection but
remain same type when called on a non option collection.
How would flatMap be implemented if would have been stand alone?
This for ex. I can't get to compile:
func flatMap<ElementOfResult, Element, T: Sequence>(on: T, _ transform: (
Element) throws -> ElementOfResult?
) rethrows -> [ElementOfResult] {
var result: [ElementOfResult] = []
for element in on {
if let newElement = try transform(element) {
result.append(newElement)
}
}
return result
}
Additionally please see 2 related SO questions, for background.
http://stackoverflow.com/q/42213656
http://stackoverflow.com/q/42214880
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