sub_arctic.constraints
Class external_constraint

java.lang.Object
  |
  +--sub_arctic.constraints.external_constraint

Direct Known Subclasses:

linear_ext_constraint, std_ext_constraint

public abstract class external_constraint

extends java.lang.Object

implements value_provider, value_consumer

This abstract class provides that base class for all "external" (aka heavyweight) constraints. External constraints can provide values from any source capable of supporting this protocol (which includes operations attaching and detaching dependency edges, retrieving or computing a value, and indicating the stored or computed value has been changed).

Field Summary

protected boolean	_doing_ood Local mark for breaking cycles.
protected java.util.Vector	_notify_list The set of things we notify when values are out-of-date.

Constructor Summary

external_constraint()
Default constructor.

Method Summary

void	attach_dependent(int on_part_num, value_consumer dep_obj, int dep_part) Register something as interested in (dependent on) one of the parts of this object.
void	detach_dependent(int on_part_num, value_consumer dep_obj, int dep_part) Remove an (object,part) pair from the dependent (interested in) list.
abstract java.lang.Object	get_value(int part_number) Compute an up-to-date copy of (or reference to) the value produced by this constraint.
void	value_ood(int for_part_here, value_provider prov_obj, int prov_part) Indicate to this constraint that a value it depends on (a part of a value_provider object that it is interested in) has, or might have, changed value.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

_doing_ood

protected boolean _doing_ood

Local mark for breaking cycles. This is true while a mark out-of-date traversal which has passed through this constraint is still going on. if the traversal reaches a constraint with this value set it indicates a cycle.

_notify_list

protected java.util.Vector _notify_list

The set of things we notify when values are out-of-date. This Vector contains consumer_part_ref objects.

Constructor Detail

external_constraint

public external_constraint()

Default constructor.

Method Detail

get_value

public abstract java.lang.Object get_value(int part_number)

Compute an up-to-date copy of (or reference to) the value produced by this constraint. Here part_number is ignored since we only provide one value. This gets overridden to provide the actual computation done by this constraint.

Specified by:

get_value in interface value_provider

Parameters:

int - part_number the internal part number for the value desired. In this case only part 0 is supported, so this is ignored.

attach_dependent

public void attach_dependent(int on_part_num,
                             value_consumer dep_obj,
                             int dep_part)

Register something as interested in (dependent on) one of the parts of this object. The entity registered is a part within a value_consumer object. Whenever a value represented by this value_provider changes (or might change), the value_ood() method must be invoked on each currently registered (object,part). Here we ignore on_part_num since we only have one part.

Specified by:

attach_dependent in interface value_provider

Parameters:

int - on_part_num the part of this object we are attaching the dependent to (in this case ignored since we only have one part).

value_consumer - dep_obj the dependent object.

int - dep_part the part within that object which is dependent.

detach_dependent

public void detach_dependent(int on_part_num,
                             value_consumer dep_obj,
                             int dep_part)

Remove an (object,part) pair from the dependent (interested in) list. Here we ignore on_part_num since we only have one part.

Specified by:

detach_dependent in interface value_provider

Parameters:

int - on_part_num the part number of this object the dependent was attached to (ignored here).

value_consumer - dep_obj the previously dependent object.

int - dep_part the previously dependent part of that object.

value_ood

public void value_ood(int for_part_here,
                      value_provider prov_obj,
                      int prov_part)

Indicate to this constraint that a value it depends on (a part of a value_provider object that it is interested in) has, or might have, changed value. Here we just pass this on to others that depend on us (being sure to break any cycles).

Specified by:

value_ood in interface value_consumer

Parameters:

int - for_part_here the part of this object interested in the value (here this is ignored since we only have one part).

value_provider - prov_obj the object providing the value we are interested in.

int - prov_part the part of the above object we are interested in.