title: R foreach with .combine=rbindlist
body: <p>I am using foreach with a .combine = rbindlist. This does not appear to work, although it works fine if I use .combine = rbind.</p>
  
  <p>Just to illustrate using a simple example --</p>
  
  <pre><code>&gt; t2 &lt;- data.table(col1=c(1,2,3))
  &gt; foreach (i=1:3, .combine=rbind) %dopar% unique(t2)
     col1
  1:    1
  2:    2
  3:    3
  4:    1
  5:    2
  6:    3
  7:    1
  8:    2
  9:    3
  
  # But using rbindlist gives an error
  
  &gt; foreach (i=1:3, .combine=rbindlist) %dopar% unique(t2)
  error calling combine function:
  &lt;simpleError in fun(result.1, result.2): unused argument(s) (result.2)&gt;
  NULL
  </code></pre>
  
  <p>Has anyone been able to make this work ?</p>
  
  <p>Thanks in advance.</p>