title: Concise notation for single arg anonymous function (avoiding underscore) not working as expected
body: <p>After going through some examples on the web I realize that there is a way to write an anonymous function without the underscore when only a single arg.  Also, I'm experimenting with the "span" method on List, which I never knew existed.  Anyway, here is my REPL session:</p>
  
  <pre><code>scala&gt; val nums = List(1, 2, 3, 4, 5)
  nums: List[Int] = List(1, 2, 3, 4, 5)
  
  scala&gt; nums span (_ != 3)
  res0: (List[Int], List[Int]) = (List(1, 2),List(3, 4, 5))
  
  scala&gt; nums span (3 !=)
  res1: (List[Int], List[Int]) = (List(1, 2),List(3, 4, 5))
  </code></pre>
  
  <p>So far so good.  But when I try to use the "less than" operator:</p>
  
  <pre><code>scala&gt; nums span (_ &lt; 3)
  res2: (List[Int], List[Int]) = (List(1, 2),List(3, 4, 5))
  
  scala&gt; nums span (3 &lt;)
  res3: (List[Int], List[Int]) = (List(),List(1, 2, 3, 4, 5))
  </code></pre>
  
  <p>Why is this behaving differently?</p>