title: Is it possible to use results of loops in openscads quicksort()
body: <p>Arrays openScad : I need to use the results of nested loops in quicksort() function but it seems impossible.</p>
  
  <p>'arr' in second last line (in code below) will not contain more than one value at a time. In the first run of the loop arr gets the value 2.01, in second run the value is 1.6125, and so on.
   What I need is an array containing all four values in this way: arr=[[2.01],[1.6125],[3.775],[4.8]], 
   because quicksort above needs such an input.
   If is it possible to achieve that in openScad, how do I do it?</p>
  
  <pre><code>function quicksort(arr) = !(len(arr)&gt;0) ? [] : let(
  pivot   = arr[floor(len(arr)/2)],
  lesser  = [ for (y = arr) if (y  &lt; pivot) y ],
  equal   = [ for (y = arr) if (y == pivot) y ],
  greater = [ for (y = arr) if (y  &gt; pivot) y ]
  ) concat(quicksort(lesser), equal, quicksort(greater));
  
  x_0=262; y_0=140; x_1=17.5;y_1=305;x_2=500;y_2=255; x_3=575;y_3=385;
  
  ads=[[x_0,y_0],[x_1,y_1],[x_2,y_2],[x_3,y_3]];
  for(b=[0 : 3])
  {
   for(c=[0:0])
      if(ads[b][0]&gt;=0 &amp;&amp; ads[b][1]&gt;=0)
      {         
              asc_diff=((ads[b][0])+ads[b][1])/2*0.01;                    
              arr=asc_diff; 
              //quicksort(arr) ;          
              echo("27: arr", arr); 
        }
   }
  </code></pre>