STL Templates _MULTIMAP_ Smart pointers as key values

Type of key value for map

-Can be a custom type (object, function pointer, smart pointer 、。。。 ）

-but there are side effects-a variety of problems arise when you define a type key value that cannot be sorted by the system's own < or >.

-so you need to define your own comparator for processing

Solve:

-If the key value is an object type

-You can overload the < or > operator yourself in a class

-You do not need to overload the = =

-Because the ordering of the elements is based on <, and the > is compared

eg

-a > B is b <= A;

-This is a bit of a question. I want to add ....

classkey{ Public: Key (intival): _ival (ival) {}int_ival;};BOOL operator< (Constkey& left,Constkey&Right ) {        //return Left._ival < Right._ival;     return false; //if always return False, Amap.size () is always 1. Any data coming in is/a >= b && b >= a so it's always equal.}

-When we are unable to modify the class, we can process the comparison function in the class for external use

-This is a bit of a question. I want to add ....

eg

bool Compare (constconst sale_item& RHS) {     return Lhs.book <  bool (*COMP) (constconst sale_item&

Reference:

-http://www.zhihu.com/question/34290683?sort=created

-http://blog.csdn.net/ultrahook/article/details/8146529

-http://bbs.csdn.net/topics/360183804

STL Template _MULTIMAP_ Smart pointer as key value