自定义结构类型,为支持插入到stl set或者排序,一种方式是重载operator<运算符成员函数.如果忘记将函数标识为const,则在编译时会报
6>c:\program files (x86)\microsoft visual studio 10.0\vc\include\xfunctional(125): error C2678: binary ‘<‘ : no operator found which takes a left-hand operand of type ‘const YourOwnItem‘ (or there is no acceptable conversion)
将函数改为const即可
原文：http://www.cnblogs.com/RoamSpace/p/5537967.html