anchor.diff:                  ]
               )
           |+> Static (   // xhr section
  -                // approximate: need xhr-returning API (TODO)
  +                // approximate: need xhr-returning API
                   // note: turns out d3 detects callback arity dynamically, and calls it differently!
                   // therefore need extra care with tupled functions.
                   let remote name t : list<CodeModel.IClassMember> =
  
positive.code: 
              //sets
  
              
          ]
          |+> Static (
                  // interpolation section
  
negative.code:                     "insert"     => chained (nameArg * !?(String + selectionCallback Element)?before)
                      "remove"     => chained O
  
                      "datum"      => chained (Obj + selectionCallback Obj)?value
                      "filter"     => chained (String + selectionCallback Bool)?selector
                      "sort"       => chained !?Comparator?comparator
  