public static CommonNoun LeastUpperBound(CommonNoun a, CommonNoun b)
{
if (a == null)
{
return(b);
}
if (b == null)
{
return(a);
}
if (a.IsSuperKindOf(b))
{
return(a);
}
foreach (var super in a.Superkinds)
{
var lub = LeastUpperBound(super, b);
if (lub != null)
{
return(lub);
}
}
return(null);
}
public bool IsSubKindOf(CommonNoun super) => super.IsSuperKindOf(this);