// bind1st和bind2nd函式把一個二元函式物件繫結成為一個一元函式物件。
// 但是由於二元函式物件接受兩個引數，在繫結成為一元函式物件時需要將原來兩個引數中的一個繫結下來。
// 也即通過繫結二元函式物件的一個引數使之成為一元函式物件的。
// bind1st是繫結第一個引數，bind2nd則是繫結第二個引數。
// 我個人喜歡用bind2nd，這樣子程式碼讀起來更順。

class greaterthan5: std::unary_function<int, bool>
{
public:
	result_type operator()(argument_type i)
	{
		return (result_type)(i > 5);
	}
};

void test_func_bind()
{
	std::vector<int> v1;
	std::vector<int>::iterator Iter;

	int i;
	for (i = 0; i <= 5; i++)
	{
		v1.push_back(5 * i);
	}

	std::cout << "The vector v1 = ( " ;
	std::copy(v1.cbegin(), v1.cend(), std::ostream_iterator<int>(std::cout, " "));
	std::cout << ")" << std::endl;

	// Count the number of integers > 10 in the vector
	std::vector<int>::iterator::difference_type result1a;
	result1a = count_if(v1.begin(), v1.end(), bind1st(std::less<int>(), 10));
	std::cout << "The number of elements in v1 greater than 10 is: "
		<< result1a << "." << std::endl;

	// Compare: counting the number of integers > 5 in the vector
	// with a user defined function object
	std::vector<int>::iterator::difference_type result1b;
	result1b = count_if(v1.begin(), v1.end(), greaterthan5());
	std::cout << "The number of elements in v1 greater than 5 is: "
		<< result1b << "." << std::endl;

	// Count the number of integers < 10 in the vector
	std::vector<int>::iterator::difference_type result2;
	result2 = count_if(v1.begin(), v1.end(), bind2nd(std::less<int>(), 10));
	std::cout << "The number of elements in v1 less than 10 is: "
		<< result2 << "." << std::endl;
}