Aspect oriented programming: Difference between revisions

=={{header|Ada}}==

The primary unit of modularity in Ada is the package. Ada provides the ability to create child packages with visibility into portions of their parent package without modifying the parent package. The child package can provided extended capabilities based upon the data types, data elements and subprograms defined in the parent package.

Example parent package specification:

<lang Ada>package parent is

function Add2 (X : in Integer) return Integer;

end parent;</lang>

Example parent package body:

<lang Ada>package body parent is

function Add2 (X : in Integer) return Integer is

begin

return X + 2;

end Add2;

end parent;</lang>

Example child package specification:

<lang Ada>package parent.child is

function Add2 (X : in Integer) return Integer;

end parent.child;</lang>

Example child package specification:

<lang Ada>with Ada.Text_IO; use Ada.Text_IO;

package body parent.child is

function Add2 (X : in Integer) return Integer is

begin

Put_Line ("Added 2 to " & X'Image);

return parent.Add2 (X);

end Add2;

end parent.child;</lang>

The following program demonstrates calling both the Add2 function from the parent package and calling the Add2 function from the child package. The child package has visibility to the public portion of the parent package and can therefore call the parent's Add2 function directly.

<lang Ada>with parent.child;

with Ada.Text_IO; use Ada.Text_IO;

procedure Main is

Num : Integer := 5;

Result : Integer;

begin

Put_Line ("Calling parent Add2 function:");

Result := parent.Add2 (Num);

Put_Line ("Result : " & Result'Image);

New_Line;

Put_Line ("Calling parent.child Add2 function");

Result := parent.child.Add2 (Num);

Put_Line ("Result : " & Result'Image);

end Main;</lang>

{{output}}

<pre>

Calling parent Add2 function:

Result : 7

Calling parent.child Add2 function

Added 2 to 5

Result : 7

</pre>