code: function Variable(name, initialValue) {
    this.value = initialValue || 0;
    this.constraints = new OrderedCollection();
    this.determinedBy = null;
    this.mark = 0;
    this.walkStrength = Strength.WEAKEST;
    this.stay = true;
    this.name = name;
  }
docs: /* --- *
  V a r i a b l e
  --- 
  A constrained variable. In addition to its value, it maintain the
  structure of the constraint graph, the current dataflow graph, and
  various parameters of interest to the DeltaBlue incremental
  constraint solver.