title: Efficient way to check if a traversable has more than 1 element in Scala
body: <p>I need to check if a <code>Traversable</code> (which I already know to be <code>nonEmpty</code>) has a single element or more.</p>
  
  <p>I could use <code>size</code>, but (tell me if I'm wrong) I suspect that this could be O(n), and traverse the collection to compute it.</p>
  
  <p>I could check if <code>tail.nonEmpty</code>, or if <code>.head != .last</code></p>
  
  <p>Which are the pros and cons of the two approaches? Is there a better way? (for example, will <code>.last</code> do a full iteration as well?)</p>