Aggregate to fill part of an array but leaving a range to the default value

[OneWingedShark]

This came up in another thread, dealing with strings, from someone coming from Turbo Pascal; so I’d typed up a bit of an example on how to implement TP-style strings., note the first "+"-function:

@OneWingedShark

   Type String is record
      Length : Byte:= 0;
      Text   : Standard.String(1..255):= (others => ASCII.NUL);
   end record
   with Size => 256 * Byte'Size;
   -- Convert to/from Internal.String via unchecked conversion.

   Function "+"( Input : Standard.String ) return String is
   ( Length => Byte(Input'Length),
     Text   => Input & (Input'Length+1..256 => ASCII.NUL)
    );
   Function "+"(Input : String) return Standard.String is
   ( Input.Text(1..Input.Length) );