Object-oriented Software in Ada 95

Persistence 283
with Ada.Strings.Unbounded, Ada.Finalization;
use Ada.Strings.Unbounded, Ada.Finalization;
generic
type Index is private; --Index for record
type Data is private; --Data for record
with function ">"( F:in Index; S:in Index ) return Boolean;
package Class_Pic is
Not_There, Mainists, Per_Error : exception; --Raised Exceptions
type Pic is new Limited_Controlled with private;
procedure Initialize( The:in out Pic );
procedure Initialize( The:in out Pic; Id:in String );
procedure Finalize( The:in out Pic );
procedure Discard( The:in out Pic );
procedure Set_Name( The:in out Pic; Id:in String );
function Get_Name( The:in Pic ) return String;
procedure Add( The:in out Pic; I:in Index; D:in Data );
procedure Extract( The:in out Pic; I:in Index; D:in out Data );
procedure Update( The:in out Pic; I:in Index; D:in out Data );
private
type Leaf;
--Index + Data
type Subtree is access Leaf; --
type Pic is new Limited_Controlled with record
Tree : Subtree := null; -- Storage
Obj_Id : Unbounded_String; -- Name of object
end record;
function Find( The:in Subtree; I:in Index) return Subtree;
procedure Release_Storage( The:in out Subtree );
end Class_Pic;
Note:
The declaration of the type leaf is a forward declaration so that the type Subtree, a pointer to a
leaf can be declared. The type leaf is fully declared in the package body.
The two generic parameters, Index and Data represent the type of the index used to access the stored data.
As this generic class will need to compare indices for ">" to establish the position of an index in the binary tree, a
definition for ">" must be provided by the user of the class. Remember, the index may be of a type for which the
operation ">" is not defined between two instances of Index. This forces the user of the package to provide
implicitly or explicitly an implementation for the comparison function ">".
The implementation of the class Pic uses the data structure Element to hold the index and the data
associated with the index. The data structure Leaf represents a leaf of the binary tree which is composed of a left
and right pointer plus the data structure Element.
with Unchecked_Deallocation, Sequential_Io;
package body Class_Pic is
type Element is record --
S_Index: Index; --The Index
S_Data : Data; --The Data
end record;
type Leaf is record --
Left : Subtree; --Possible left node
Rec : Element; --Index + data
Right : Subtree; --Possible right node;
end record;
© M A Smith - May not be reproduced without permission