binary_function的问题

[erictb]

////////////////////////////////////////////
//
// Compile options needed: /GX
//
// binfunc.cpp : Illustrating the binary_function
// structure.
//
// Structure used: binary_function<A,B,C> - base
// class used to create operator
// functions taking data types A
// and B and returning data type C.
////////////////////////////////////////////

#include <functional>
#include <iostream>

using namespace std ;

class binary_test : public binary_function<binary_test &,int,float>
{
public:
float value;
binary_test(){value=10.0;}
binary_test(float x){value=x;}
result_type operator<<(second_argument_type arg2);
};

binary_test::result_type
binary_test::operator<<(binary_test::second_argument_type arg2)
{
value = ((int)value) << arg2;
cout << "New value after shift is" << value << endl;
return value;
}

void main(void)
{
binary_test item;

cout << "Begin" << endl;
item = item << 2;
///这里item << 2的返回值的类型是float，但这个表达式的左边是binary_test，这里怎么没有编译出错呢？
}

[xqk]

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