OneWingedShark

    -- Here we define an index-type with one value.
    Subtype Boolean_Index is Boolean range True..True;
    -- And here we define an array indexed by it, but can also have length 0.
    Type Optional(Boolean_Index range <>) of Element;

    Package Geometry is
       Type Point is private;
       Function  Create( X, Y : Integer ) return Point;
       Function  X( Object : Point ) return Integer;
       Function  Y( Object : Point ) return Integer;
       Procedure X( Object : in out Point; Value : Integer );
       Procedure X( Object : in out Point; Value : Integer );
    Private
       Type Point is record
          Data_X, Data_Y : Real:= 0.0;
       end record;
    
       Function  X     ( Object : Point ) return Integer is (Object.Data_X);
       Function  Y     ( Object : Point ) return Integer is (Object.Data_X);
       Function  Create( X, Y : Integer ) return Point   is
         ( Data_X => X, Data_Y => Y);
    End Geometry;

    Generic
       Type Item is private;
       One : Item;
       with "*"(Left, Right : Item) return Item is <>;
    Function Generic_Exponent( Base : Item; Exponent : Natural ) return Item;
    -- ...implementation
    Function Generic_Exponent( Base : Item; Exponent : Natural ) return Item is
     (case Exponent is
        when 0 => One,
        when 1 => Base,
        when 2 => Base*Base,
        when others =>
          -- Rule: X**2k = (X**k)**2; X**2k+1 = (X**k)**2 * X.
          (Generic_Exponent(Base, Generic_Exponent(Base, Exponent/2), 2)
            *  (if Exponent mod 2 = 1 then Base else One);
     );

    Type Temperature is range -40..2_000;
    Type Probe_Range is new Temperature range -20..200;

    (See above; note how we're depending on the type, a "one value", and a "multiply" operation.)

    Type Base is null record;
    Function Text(Object : Base) return String is ("[]");
    
    Type Color is ( Red, Green, Blue, Black, White );
    Type Colored_Thing is new Base with record
       Color_Data : Color := Red;
    end record;
    
    Function Text(Object : Colored_Thing) return String is
      ('[' & Color'Image(Object.Color_Data) & " ]");

    -- Gets text from user.
    Function Prompt return String; -- def elsewhere.
    -- Gets a previously saved object.
    Function Get( Name : String ) return Base'Class; -- def elsewhere.
    Unknown_From_User : Base'Class renames Get( Prompt );
    --...
    -- The following will print "[]" if it is BASE, and
    -- "[ COLOR ]" when COLORED_THING, replacing 'COLOR' with
    -- the textual representation/literal for the value.
    Ada.Text_IO.Put_Line( Unknown_From_User.Text );

    Ada.Text_IO.Create (
        File => File,
        Mode => Ada.Text_IO.Out_File,
        Name => "test.txt",
        Form => "shared=no"
      );

    Package Dependency is
       Package OS is
          Function Separator return String;
       End OS;
    End Dependency;
    -- ...
    Package Dependency is
       Package body OS is separate;
    End Dependency;

    -- Windows
    separate (Dependency)
    Package OS is
      Function Separator return String is ("\");
    End OS;

    -- Classic Mac
    separate (Dependency)
    Package OS is
      Function Separator return String is (":");
    End OS;

    -- VMS
    separate (Dependency)
    Package OS is
      Function Separator return String is (".");
    End OS;

    -- UNIX-like
    separate (Dependency)
    Package OS is
      Function Separator return String is ("/");
    End OS;

    Generic
      Type Index   is (<>);                                      -- Any discrete type.
      Type Element is limited private;                           -- Any non-discriminated type.
      Type Vector  is array(index range <>) of element;          -- An array-type of Element, indexed by Index.
      with Function "="(Left, Right: Element) return Boolean <>; -- Equal, defaulted.
      with Function "<"(Left, Right: Element) return Boolean <>; -- Less-than, defaulted.
    Function Generic_Sort( X : Vector ) return Vector;

    Function Sort is new Generic_Sort( Index => Integer, Element => Integer, Vector => Integer_Array, "<" => ">");

    Function Example (X : Interfaces.Unsigned_16) return Boolean
      with Import, Convention => COBOL, Link_Name => "xmpl16";

    Subtype Numeric is String
      with Dynamic_Predicate => (for all C of Numeric => C in '0'..'9'),
           Predicate_Falure  => raise Constraint_Error with "'" & Numeric &"' is not numeric.";
    --...
    Count : Numeric renames Get_User_Value;
    --...
    return Query("SELECT \* FROM Some_Table WHERE Count=" & Count & ";");

  PACKAGE Example IS
    -- The only way to get a value of ESCAPED_STRING is via calling Create.
    Type Escaped_String is private;
    Function Create( X:String ) return Escaped_String;
  PRIVATE
    Type Escaped_String is new String;
    Function Create( X:String ) return Escaped_String is
    ( SQL_Escape(X) );
  END Example;

    Text : Constant String := Read_Chapter( Book );