title: What's the deal with all the Either cruft?
body: <p>The Either class seems useful and the ways of using it are pretty obvious. But then I look at the API documentation and I'm baffled:</p>
  
  <pre><code>def joinLeft [A1 &gt;: A, B1 &gt;: B, C] (implicit ev: &lt;:&lt;[A1, Either[C, B1]]):
           Either[C, B1]
     Joins an Either through Left.
  
  def joinRight [A1 &gt;: A, B1 &gt;: B, C] (implicit ev: &lt;:&lt;[B1, Either[A1, C]]):
           Either[A1, C]
     Joins an Either through Right.
  
  def left : LeftProjection[A, B]
     Projects this Either as a Left.
  
  def right : RightProjection[A, B]
     Projects this Either as a Right.
  </code></pre>
  
  <p>What do I do with a projection and how do I even <em>invoke</em> the joins?</p>
  
  <p>Google just points me to the API documentation.</p>
  
  <p>This might just be a case of "paying no attention to the man behind the curtain", but I don't think so. I think this is important.</p>