bind1st Function

创建一个适配器转换为二进制函数对象转换为一元求函数对象通过将二进制功能第一个参数为指定值的帮助器模板函数。

template<class Operation, class Type>
   binder1st <Operation> bind1st(
      const Operation& _Func, 
      const Type& _Left
   );

参数

• _Func
  要转换的二进制函数对象转换为一元求函数对象。

• _Left
  二进制函数对象第一个参数将绑定的值。

返回值

一元求函数对象从绑定二进制函数对象的第一个参数的结果传递到值的 _Left.

备注

功能联编程序是功能，适配器，因为它们返回函数对象，可用于函数组合的某些类型构造更为复杂强大的表达式。

如果 _Func 是类型 Operation 对象，并 c 是常数，则 bind1st (_Func，c)。binder1st 选件类构造函数 binder1st<Operation> (_Func，c)等效可以更方便。

示例

// functional_bind1st.cpp
// compile with: /EHsc
#include <vector>
#include <functional>
#include <algorithm>
#include <iostream>

using namespace std;

// Creation of a user-defined function object
// that inherits from the unary_function base class
class greaterthan5: unary_function<int, bool>
{
public:
    result_type operator()(argument_type i)
    {
        return (result_type)(i > 5);
    }
};

int main()
{
    vector<int> v1;
    vector<int>::iterator Iter;

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

    cout << "The vector v1 = ( " ;
    for (Iter = v1.begin(); Iter != v1.end(); Iter++)
        cout << *Iter << " ";
    cout << ")" << endl;

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

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

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

要求

标头: <functional>

命名空间: std

请参见

参考

标准模板库