consider supporting default values (simple or expressions) in primitive operations

[abstratt]

For instance:

class String specializes Primitive
  query isEmpty() : Boolean;
  query size() : Integer;
  query add(s : String[0,1] := "") : String;
  query add(s : any[0,1] := "") : String;
  query substring(start : Integer[1] := 0,stop : Integer[1] := { self.size() }) : String;
  query toLower() : String;
  query toUpper() : String;
  query contains(another : String[1] := "") : Boolean;
end;