Editing Generic programming (section)

=====Example=====
The specification of a generic package:

<syntaxhighlight lang="ada">
 generic
    Max_Size : Natural; -- a generic formal value
    type Element_Type is private; -- a generic formal type; accepts any nonlimited type
 package Stacks is
    type Size_Type is range 0 .. Max_Size;
    type Stack is limited private;
    procedure Create (S : out Stack;
                      Initial_Size : in Size_Type := Max_Size);
    procedure Push (Into : in out Stack; Element : in Element_Type);
    procedure Pop (From : in out Stack; Element : out Element_Type);
    Overflow : exception;
    Underflow : exception;
 private
    subtype Index_Type is Size_Type range 1 .. Max_Size;
    type Vector is array (Index_Type range <>) of Element_Type;
    type Stack (Allocated_Size : Size_Type := 0) is record
       Top : Index_Type;
       Storage : Vector (1 .. Allocated_Size);
    end record;
 end Stacks;
</syntaxhighlight>

Instantiating the generic package:

<syntaxhighlight lang="ADA">
 type Bookmark_Type is new Natural;
 -- records a location in the text document we are editing

 package Bookmark_Stacks is new Stacks (Max_Size => 20,
                                        Element_Type => Bookmark_Type);
 -- Allows the user to jump between recorded locations in a document
</syntaxhighlight>

Using an instance of a generic package:

<syntaxhighlight lang="ada">
 type Document_Type is record
    Contents : Ada.Strings.Unbounded.Unbounded_String;
    Bookmarks : Bookmark_Stacks.Stack;
 end record;

 procedure Edit (Document_Name : in String) is
   Document : Document_Type;
 begin
   -- Initialise the stack of bookmarks:
   Bookmark_Stacks.Create (S => Document.Bookmarks, Initial_Size => 10);
   -- Now, open the file Document_Name and read it in...
 end Edit;
</syntaxhighlight>