anchor.diff:    ;
   
   discrete_range
  -  : range
  +  : range_decl
     | subtype_indication
     ;
   
  
positive.code:   : quantity_list COLON name
    ;
  
  range
    : explicit_range
    | name
    ;
  
negative.code:   ;
  
  range_constraint
    : RANGE range_decl
    ;
  
  record_nature_definition
  