llapse" id="comment-func-element_-sequence-joined_"><div class="p">
    <p>Returns the concatenated elements of this sequence of sequences,
inserting the given separator between each element.</p>

<p>This example shows how an array of <code>[Int]</code> instances can be joined, using
another <code>[Int]</code> instance as the separator:</p>

<pre><code class="language-swift">let nestedNumbers = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
let joined = nestedNumbers.joined(separator: [-1, -2])
print(Array(joined))
// P