Ada Reference Manual (Ada 2022)
12.5.5 Formal Interface Types
The category determined for a formal interface type is the category of all interface types.
Syntax
Legality Rules
The actual type shall be a descendant of every progenitor of the formal type.
The actual type shall be a limited, task, protected, or synchronized interface if and only if the formal type is also, respectively, a limited, task, protected, or synchronized interface.
Examples
Example of the use of a generic with a formal interface type, to establish a standard interface that all tasks will implement so they can be managed appropriately by an application-specific scheduler:
type Root_Work_Item is tagged private;
generic
type Managed_Task is task interface;
type Work_Item(<>) is new Root_Work_Item with private;
package Server_Manager is
task type Server is new Managed_Task with
entry Start(Data : in out Work_Item);
end Server;
end Server_Manager;
type Managed_Task is task interface;
type Work_Item(<>) is new Root_Work_Item with private;
package Server_Manager is
task type Server is new Managed_Task with
entry Start(Data : in out Work_Item);
end Server;
end Server_Manager;
