
suspend(+Goal, +Prio, +CondList, -Susp)

   Delay the Goal as suspension Susp and wake it with priority Prio
as soon as one of the specifications in CondList occurs.



Arguments
   Goal                A callable term.
   Prio                An integer.
   CondList            A term of the form Vars->Cond or trigger(Atom) or a list of such terms.
   Susp                A free variable used to return the created suspension.

Type
   Advanced Control and Suspensions

Description
   The specified goal Goal is suspended (a suspension is created and
   returned as Susp) and it is woken with the priority Prio as soon as
   one trigger conditions specified in CondList arises.

   The Prio argument determines the priority with which the Goal will be
   scheduled when woken. It can be a positive number between 1 and 12,
   or zero, in which case the priority defaults to the priority setting
   of the predicate which is called in Goal.

   CondList is one term or a list of terms of the form Vars->Cond.
   The condition Cond is either the name of a predefined suspension
   list or the specification of a suspension list in one of the
   variable's attributes.  The predefined suspension lists are inst
   (for instantiation), bound (bound to another variable) and constrained
   (any constraining attribute modification).
   The general specification has the form



    Vars->moduleName:(suspListName of attrStruct)

    which can be abbreviated (if moduleName and attrStruct are identical) to



    Vars->moduleName:suspListName

    The following are examples for valid conditions:



    Vars->inst
    Vars->constrained
    Vars->fd:min
    Vars->fd:(min of fd)

   A specification of the form trigger(Atom) states that the goal should
   be woken by a symbolic trigger, ie.  by a matching invocation of the
   built-in schedule_suspensions/1.  The name of the trigger can be an
   arbitrary atom.




Modes and Determinism
   suspend(+, +, +, -) is det

Modules
   This predicate is sensitive to its module context (tool predicate, see @/2).

Exceptions
     6 --- CondList is ill-formed.

Examples
   
[eclipse]: suspend(writeln(hello), 2, X->inst, Susp),
        get_suspension_data(Susp, goal, Goal),
        get_suspension_data(Susp, module, Module).

X = X
Goal = writeln(hello)
Susp = 'SUSP-_321-susp'
Module = eclipse

Delayed goals:
        writeln(hello)
yes.

[eclipse]: suspend(writeln(hello), 2, X->inst, Susp),
        kill_suspension(Susp),     % killed before woken
	X=1.

Susp = 'SUSP-_308-dead'
X = 1
yes.


See Also
   demon / 1, make_suspension / 3, insert_suspension / 3, suspend / 3, attach_suspensions / 2
