/// <summary> Adds a constraint to this network.
/// If the constraint is already in the nework, this invocation has no effect.
/// Please notice that variables in the constraint are not automatically added.
/// </summary>
/// <param name="c">the constraint to be added
/// </param>
/// <returns> the constraint itself
/// </returns>
/// <throws> NullPointerException if <tt>c</tt> is <tt>null</tt> </throws>
/// <throws> IllegalArgumentException if <tt>c</tt> is already added to another network </throws>
protected internal virtual Constraint ADD(Constraint c)
{
if (!_constraints.Contains(c))
{
if (c.Index >= 0)
{
throw new ArgumentException();
}
c.Index = _constraints.Count;
_constraints.Add(c);
}
return c;
}
public ConstraintToken(Constraint value)
{
_value = value;
}