Another solution is to use the Ada.Text_IO.Editing package.
This package is able to format decimal number with great simplicity
(the functionalities are derived from the COBOL pictures) and is
very powerfull.

This is maybe a complex solution for a simple problem but in some
others complex cases it is very usefull.

-----------------------------------------

with Ada.Text_IO.Editing;

procedure Zfill is

   use Ada;

   type Num is delta 0.1 digits 10;

   package Text_Editing is new Text_IO.Editing.Decimal_Output (Num);

   X : Integer := 2;

begin
   Text_Editing.Put (Num (X), Pic => Text_IO.Editing.To_Picture ("999"));
end Zfill;

--

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