I am working with sets of pairs of integers in Rust using HashSet<(usize, usize)>, and my goal is to compute a set HashSet<usize> which contain all nodes appearing in those pairs. Essentially, this is a flatten operation.
Let's suppose variable set: HashSet<(usize, usize)> contains the initial set of pairs. My first attempt to compute the flattened version was:
let res: HashSet<usize> = set.iter().flatten().collect()
however I encounter the error: "&(usize, usize) is not an iterator the trait Iterator is not implemented for &(usize, usize) required for &(usize, usize) to implement IntoIterator. Required by a bound in flatten."
I thought the issue was that the iterator was over references so I also tried using into_iter instead, but I get the same error message, this time saying "(usize, usize) is not an iterator..."
I do have a piece of code that works fine using a for loop and the push operation, but I would like to do it in a more functional way with flatten.
Simply convert the tuple to an array, which is iterable:
let res: HashSet<usize> = set.iter().flat_map(|&(a, b)| [a, b]).collect();