title: Haskell pattern matching a list of tuples
body: <p>As the post title says, I'm defining the following function in Haskell:</p>
  
  <pre><code>prop_LeftInverse :: (Eq a, Eq b) =&gt; [(a,b)] -&gt; Bool
  prop_LeftInverse (x,y):(xs,ys) = undefined
  </code></pre>
  
  <p>which should take as input a list of tuples. I'm getting a <code>parse error in pattern</code> but I can't quite figure out what it is, and also haven't found any information about this specific case...</p>