title: How to use cats typeclasses?
body: <pre><code>import cats._
  import cats.data._
  import cats.implicits._
  import cats.instances.all._
  
  ...
    def test = Foldable[List].intercalate(List("a", "b", "c"), "-")
  ...
  </code></pre>
  
  <p>results into:</p>
  
  <pre><code>could not find implicit value for parameter instance: cats.Foldable[List]
  </code></pre>
  
  <p>Why it isn't working and how to fix it? It seems like it is just a copy from their docs:</p>
  
  <pre><code>scala&gt; import cats.implicits._
  scala&gt; Foldable[List].intercalate(List("a","b","c"), "-")
  res0: String = a-b-c
  </code></pre>
  
  <p>Edit 1:</p>
  
  <p>Even after removing <code>import cats.instances.all._</code> as suggested it still doesn't work. Now it crashes with:</p>
  
  <pre><code>value intercalate is not a member of cats.Foldable[List]
  </code></pre>