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From: Ludovic Brenta <ludovic@ludovic-brenta.org>
Newsgroups: comp.lang.ada
Subject: Re: What's wrong with my code?
Date: Tue, 29 Apr 2008 02:31:23 -0700 (PDT)
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> generic
>    type Element is private;
>    with procedure Element_Put(E : in Element);
> package SelectionP is

Others have explained why neither Ada.Text_IO.Put nor
Ada.Integer_Text_IO.Put are acceptable actuals for Element_Put.

Element_Put is only necessary for one subprogram (procedure Print).
Yet, all users of your package must provide an actual for Element_Put
even if they don't call Print. Similarly, Find_Min and Sort are likely
to require a function "<" to compare Elements. So I suggest:

generic
   type Element is private;
package Selection_P is
   type Index_Type is range 0 .. 10;
   type My_Array is array (Index_Type) of Element;

   generic
      with function "<" (Left, Right : in Element) return Boolean is
<>;
   procedure Find_Min (A : My_Array; Offset : in Index_Type; Pos : out
Index_Type);

   procedure Swap (A : in out My_Array; First, Second : Index_Type);

   generic
      with function "<" (Left, Right : in Element) return Boolean is
<>;
   procedure Sort (A : in out My_Array);

   generic
      with procedure Put (E : in Element) is <>;
   procedure Put (A : in My_Array);
end Selection_P;

The reason I didn't place "<" as a generic formal parameter of the
package, but rather of Find_Min and Sort, is because you might want to
find the maximum element but sort in ascending order, like this:

package S is new Selection_P (Element => Integer);
procedure Find_Max is new S.Find_Min ("<" => ">"); -- use ">" as the
actual
procedure Sort is new S.Sort; -- use the default "<", sort in
ascending order
procedure Put (J : in Integer) is
begin
   Ada.Integer_Text_IO.Put (J);
end Put;
procedure Put is new S.Put; -- use the default

HTH

--
Ludovic Brenta.