Scala SeqLike distinct preserves order?

Question

The apidoc of distinct in SeqLike says:

Builds a new sequence from this sequence without any duplicate elements. Returns: A new sequence which contains the first occurrence of every element of this sequence.

Do I feel it correct that no ordering guarantee is provided? More generally, do methods of SeqLike provide any process-in-order (and return-in-order) guarantee?

Answer 1

On the contrary: operations on Seqs guarantee the output order (unless the API says otherwise). This is one of the basic properties of sequences, where the order matters, versus sets, where only containment matters.

Answer 2

It depends on the collection you were using in the first place. If you had a list you'll get your order. If on the other hand you had a set, then probably not.