title: How do you assign "null" to a Delphi.net Nullable
body: <p>How do you assign null to a Delphi.net Nullable? I have a field which previously contained a value , I need to clear its value back to null.</p>
  
  <pre><code>depth : Nullable&lt;Double&gt;;
  
  Procedure ClearDepth;
  begin 
      depth := Nil;
  end;
  </code></pre>
  
  <p>The above creates the error <code>Error: E2010 Incompatible types : 'Nullable&lt;System.Double&gt;' and 'Pointer'</code>. using <code>Null</code> in place of <code>Nil</code> gives the same error with <code>Variant</code> in place of <code>Pointer</code>. I wondered if I should be using a special constructor to generate a null nullable but I couldn't see one in the documentation?</p>
  
  <p>The following works but doesn't seem like a great solution, can anyone suggest a better way?</p>
  
  <pre><code>Procedure ClearDepth;
  var
      uninitialisedValue : Nullable&lt;Double&gt;;
  begin 
      depth := uninitialisedValue;
  end;
  </code></pre>