12.5.5 Formal Interface Types
Proof: {
AI95-00442-01}
This rule follows from the rule in
12.5 that
says that the category is determined by the one given in the name of
the syntax production. The effect of the rule is repeated here to give
a capsule summary of what this subclause is about.
Ramification: Here we're taking advantage
of our switch in terminology from “determined class” to “determined
category”; by saying “category” rather than “class”,
we require that any actual type be an interface type, not just some type
derived from an interface type.
Syntax
Legality Rules
{
AI95-00251}
{
AI95-00401}
The actual type shall be a descendant of every progenitor of the formal
type.
{
AI95-00345}
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.
Discussion: We require the kind of interface
type to match exactly because without that it is almost impossible to
properly implement the interface.
Examples
{
AI12-0429-1}
{
AI12-0442-1}
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: {
AI95-00433-01}
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;
Extensions to Ada 95
Ada 2005 and 2012 Editions sponsored in part by Ada-Europe
