whole_func_string: function BinaryConstraint(var1, var2, strength) {
    BinaryConstraint.superConstructor.call(this, strength);
    this.v1 = var1;
    this.v2 = var2;
    this.direction = Direction.NONE;
    this.addConstraint();
  }
func_code_string: function BinaryConstraint(var1, var2, strength) {
    BinaryConstraint.superConstructor.call(this, strength);
    this.v1 = var1;
    this.v2 = var2;
    this.direction = Direction.NONE;
    this.addConstraint();
  }
func_documentation_string: Abstract superclass for constraints having two possible output
  variables.