title: remove elements from a list in ml
body: <p>I´m trying to write a function that produces a new list containing the given list without the element x.</p>
  
  <p>Moscow ML says that some cases are unused in this match. </p>
  
  <pre><code>fun delete (x,list) = delete(x,[])
   |delete(x,(first::rest)) = if first = x then delete(x,rest) else first::delete(x,rest)
  </code></pre>