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9.7.3 Conditional Entry Calls

(1)

A conditional_entry_call issues an entry call that is then cancelled if it is not selected immediately (or if a requeue-with-abort of the call is not selected immediately).

Syntax

(2)
       conditional_entry_call ::=
         select
          entry_call_alternative
         else
          sequence_of_statements
         end select;

Dynamic Semantics

(3)

The execution of a conditional_entry_call is defined to be equivalent to the execution of a timed_entry_call with a delay_alternative specifying an immediate expiration time and the same sequence_of_statements as given after the reserved word else.

NOTES

(4)

(37) A conditional_entry_call may briefly increase the Count attribute of the entry, even if the conditional call is not selected.

Examples

(5)

Example of a conditional entry call:

(6)
       procedure Spin(R : in Resource) is
       begin
          loop
             select
                R.Seize;
                return;
             else
                null;  --  busy waiting
             end select;
          end loop;
       end;

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