> On 19 Jun 2016, at 11:12, Haravikk via swift-evolution
> <[email protected]> wrote:
>
> I think the following should work for the generic case, and is pretty similar:
>
> extension MutableCollection {
> public mutating func remove(indices: Set<Index>) {
> var index = self.startIndex
> self = self.filter {
> let result = indices.contains(index)
> self.formIndex(after: &index)
> return result
> }
> }
> }
Apologies for the double-post but I’m honour bound to follow up that my generic
method is a load of nonsense at the moment; it’s missing some kind of
constructor (I don’t recall if there’s a common option that will satisfy this),
also, due to the way .filter {} currently works even in its lazy form it can
end up calling the filter closure more than once per item, so advancing the
index currently won’t work as expected (elements are skipped, children
murdered, it’s just the worst).
So yeah, best option to do this right now is with a proper loop over
self.indices, but it still requires some kind constructor to build a new copy
of the correct type.
For arrays this is a bit simpler as you *can* safely remove indices in reverse
order, since later indices cannot invalidate earlier ones, but this is reliant
on the array’s indices being integers (reasonable enough, but not really
correct in the strictest sense), so like so:
extension Array {
public mutating func remove(indices: Set<Index>) {
for eachIndex in indices.sort(>) { // greater than
should give descending order
self.remove(at: eachIndex)
}
}
}
But yeah, this is only safe on types where removing later items does not change
the order of earlier ones, though this should be true on Array, Dictionary and
Set since none of these shrink as elements are removed, it’s not strictly a
good idea to rely on this behaviour as it’s implementation dependent, even
though it’s unlikely this will change._______________________________________________
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