摘要： 要满足strict weak ordering 理论。strict weak ordering 理论是建立在 strict partial ordering 理论之上的。irrefective, antisymmetric,transitive(partial order 的要求)transitive of equivalence。参考http://www.sgi.com/tech/stl/StrictWeakOrdering.htmlhttp://en.wikipedia.org/wiki/Strict_weak_order 阅读全文