code: public synchronized boolean compatible(PType to, PType from)
  	{
  		done.clear();
  		return searchCompatible(to, from, false) == Result.Yes;
  	}
docs: Test whether the two types are compatible. This means that, at runtime, it is possible that the two types are the
  same, or sufficiently similar that the "from" value can be assigned to the "to" value.
  
  @param to
  @param from
  @return True if types "a" and "b" are compatible.