1.34.1 Instance variables

constraint <- from: object

Object at the specified side of the constraint. Once the constraint is established it makes no difference which object is at which side. The constraint is established by making constraint<-to consistent with constraint<-from.

The constraint may be found though object<-all_constraints from either constrained object.

constraint-locked: {none,forwards,front,backwards,back}

This variable serves two purposes: avoid loops and implement constraints that only propagate in one direction. Its values are:

forwards	Only propagate constraint<-from to constraint<-to
backwards	Only propagate constraint<-to to constraint<-from
none	Propagate both ways
front	constraint<-from has changed. Avoid loop
back	constraint<-to has changed. Avoid loop

constraint <- relation: relation

The relation that maintains the constraint. This object will be send the following messages:

relation->create	Upon establishing.
relation->forwards	constraint<-from has changed
relation->backwards	constraint<-to has changed

constraint <- to: object

Inherits description from: constraint-from