title: Scala underscore notation for map and filter
body: <p>Say I have the following code:</p>
  
  <pre><code>val a: List[(Int, String)] = List((1,"A"),(2,"B"),(3,"C"))
  val b: List[String] = List("A","C","E")
  </code></pre>
  
  <p>I can do:</p>
  
  <pre><code>a.map{case (fst,snd) =&gt; (fst,snd + "a")}
  a.filter{case (_,snd) =&gt; b.contains(snd)}
  </code></pre>
  
  <p>But why can't I do:</p>
  
  <pre><code>a.map((_._1,_._2 + "a"))
  a.filter(b.contains(_._2))
  </code></pre>
  
  <p>Is there a way to accomplish this using underscore notation, or am I forced here?</p>