schedule_suspensions(+Position, +Attribute)

Position

Integer indicating the position of the suspension list.

Attribute

Compound term, typically a variable's attribute with a suspension list in Position'th argument.

Description

The task of schedule_suspensions/2 is to take suspensions from a suspension list and schedule them for execution. The suspensions are put into a global priority list, according to their individual priority. A subsequent wake/0 will then actually execute them.

As a side effect, the suspension list within Attribute is updated, ie. suspensions which are no longer useful are removed destructively.

Modes and Determinism

• schedule_suspensions(+, +) is det

Exceptions

(4) instantiation fault

Position or Attribute is not instatiated.

(5) type error

Position is not an integer.

(5) type error

Attribute is not a structure or it Position'th argument is not a list of suspensions.

(6) out of range

Attribute does not have a Position'th argument.

Examples

[eclipse 1]: make_suspension(writeln(hello), 4, S),
             make_suspension(writeln('hi there'), 2, T),
	     Attr = attr([S,T]),
             schedule_suspensions(1, Attr),
             wake.
hi there
hello

S = 'SUSP-_306-dead'
T = 'SUSP-_311-dead'
Attr = attr([])
yes.

[eclipse 2]: [user].
 :- demon(d/0).
 d :- writeln(demon).

user       compiled traceable 68 bytes in 0.12 seconds

yes.
[eclipse 3]: make_suspension(d, 4, S), 
             make_suspension(writeln('hi there'), 2, T),
	     Attr = attr([S,T]),
	     schedule_suspensions(1,Attr),
	     wake.
hi there
demon

S = 'SUSP-_304-susp'
T = 'SUSP-_309-dead'
Attr = attr(['SUSP-_304-susp'])

Delayed goals:
        d
yes.

See Also