anchor.diff:  
   //TODO-AC: antlr periodically has trouble with this (because of unary plus?)
   plus_expr_in_array :
  -     binary_expr_in_array (t_FILLER (t_PLUS | t_MINUS) t_FILLER binary_expr_in_array | (t_PLUS | t_MINUS) t_FILLER? binary_expr_in_array)*
  +     binary_expr_in_array ((t_FILLER (t_PLUS | t_MINUS) t_FILLER | (t_PLUS | t_MINUS) t_FILLER?) binary_expr_in_array)*
     ;
   
   binary_expr_in_array :
  
positive.code: prefix_expr :
       pow_expr
    |  t_NOT t_FILLER? prefix_expr
    |  (t_PLUS | t_MINUS) t_FILLER? prefix_expr //NB: plus_expr breaks if this is written as two rules
    ;
  
  pow_expr :
  
negative.code:   ;
  
  element_list :
       element (element_separator_list element)*
    ;
  
  element :
       expr_in_array
    ;
  
  //non-empty
  