HashSet<T> to HashSet<&T>

help
1

In a function that is working with HashSet<T>s, I at some point take a union of two sets like so:

let set_union: HashSet<&T> = sets[i].union(&sets[j]).collect();

where sets is of type &Vec<HashSet<T>. This works well. However, now when I want to later take a union again, I run into a mismatched types error:

let set_union_2: HashSet<&T> = set_union.union(&sets[k]).collect();
                                               ^^^^^^^^ expected `&T`, found type parameter `T`

I suppose I can .iter() the set and then .collect() it again, but is there a better way to turn sets[k] into a set of type HashSet<&T> so that taking a union is possible?

2

You could just do set_union.extend(&sets[k]), in case you don’t need set_union anymore. Otherwise, let mut set_union2 = set_union.clone(); set_union2.extend(&sets[k]); is probably a decent option.

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3

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