Ada '83 Language Reference Manual

Copyright 1980, 1982, 1983 owned by the United States Government. Direct reproduction and usage requests to the Ada Information Clearinghouse.

9.9. Task and Entry Attributes

For a task object or value T the following attributes are defined:

• T'CALLABLE
  Yields the value FALSE when the execution of the task designated by T is either completed or terminated, or when the task is abnormal. Yields the value TRUE otherwise. The value of this attribute is of the predefined type BOOLEAN.
  
  
• T'TERMINATED
  Yields the value TRUE if the task designated by T is terminated. Yields the value FALSE otherwise. The value of this attribute is of the predefined type BOOLEAN.

In addition, the representation attributes STORAGE_SIZE, SIZE, and ADDRESS are defined for a task object T or a task type T (see 13.7.2).

The attribute COUNT is defined for an entry E of a task unit T. The entry can be either a single entry or an entry of a family (in either case the name of the single entry or entry family can be either a simple or an expanded name). This attribute is only allowed within the body of T, but excluding within any program unit that is, itself, inner to the body of T.

• E'COUNT
  Yields the number of entry calls presently queued on the entry E (if the attribute is evaluated by the execution of an accept statement for the entry E, the count does not include the calling task). The value of this attribute is of the type universal_integer.

Note:

Algorithms interrogating the attribute E'COUNT should take precautions to allow for the increase of the value of this attribute for incoming entry calls, and its decrease, for example with timed entry calls.

References: abnormal task, accept statement, attribute, boolean type, completed task, designate, entry, false boolean value, queue of entry calls, storage unit, task, task object, task type, terminated task, timed entry call, true boolean value, universal_integer type.

Rationale references: 13.2.2 Task Execution, 13.2.9 Task Types, 13.2.11 Families, Entries and Scheduling

Style Guide references: 6.2.3 Attributes 'Count, 'Callable and 'Terminated

Address any questions or comments to adainfo@sw-eng.falls-church.va.us.