Re: Aliasing or referencing assignment

["Jeffrey R. Carter" <spam@spam.com>]

David Trudgett wrote:
> Without knowing the details of how they work, I was just assuming they
> would be pre-elaborated during the compilation process.

GNAT in gcc 3.4.2 implements Unbounded_String as

    package AF renames Ada.Finalization;

    Null_String : aliased String := "";

    type Unbounded_String is new AF.Controlled with record
       Reference : String_Access := Null_String'Access;
       Last      : Natural       := 0;
    end record;

and To_Unbounded_String as

    function To_Unbounded_String (Source : String) return Unbounded_String is
       Result : Unbounded_String;

    begin
       Result.Last          := Source'Length;
       Result.Reference     := new String (1 .. Source'Length);
       Result.Reference.all := Source;
       return Result;
    end To_Unbounded_String;

Other implementations are possible.

-- 
Jeff Carter
"I'm a lumberjack and I'm OK."
Monty Python's Flying Circus
54