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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). A procedure call may appear rather than an entry call for cases where the procedure might be implemented by an entry.
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conditional_entry_call::=
select
entry_call_alternative
else
sequence_of_statements
end select;
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The execution of a conditional_entry_call is defined to be equivalent to the execution of a timed_entry_call (see 9.7.2) with a delay_alternative (see 9.7.1) specifying an immediate expiration time and the same sequence_of_statements (see 5.1) as given after the reserved word else.
NOTES
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40 A conditional_entry_call may briefly increase the Count attribute of the entry, even if the conditional call is not selected.
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Example of a conditional entry call:
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procedure Spin(R : in Resource) is begin loop select R.Seize; return; else null; −− busy waiting end select; end loop; end;