title: Difference between Left and Right
body: <p>I am currently reading the excellent "Learn You a Haskell for Great Good", and in the <a href="http://learnyouahaskell.com/functors-applicative-functors-and-monoids">section about functors</a> there is an example involving <code>Either</code> which I don't understand:</p>
  
  <pre class="lang-haskell prettyprint-override"><code>ghci&gt; fmap (replicate 3) (Right "blah")
  Right ["blah","blah","blah"]
  </code></pre>
  
  <pre class="lang-haskell prettyprint-override"><code>ghci&gt; fmap (replicate 3) (Left "foo")
  Left "foo"
  </code></pre>
  
  <p>Why is the latter not <code>Left ["foo", "foo", "foo"]</code>?</p>