The class Student 
{
Public: 
Student (void); 
~ Student (void); 
Public: 
Float _stuScore; 
//a Boolean operator overloading 
Boolean operator & lt; (const Student& Stu) 
{
Return _stuScore & lt; Stu. _stuScore; 
} 
}; 


Struct CharLess: public binary_function & lt; Const Student, const Student, bool> 
{
Public: 
Result_type operator () (const first_argument_type & amp; _Left, const second_argument_type & amp; Const _Right) 
{
Return _Left & lt; _Right; 
} 
}; 

Hash_map & lt; Const char *, int, hash_compare & lt; Const Student, CharLess> CharHash;