bind1st 函数

一个辅助模板函数，它创建一个适配器，通过将二元函数的第一个参数绑定为指定值，将二元函数对象转换为一元函数对象。

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

参数

• _Func
  要平移的二进制函数对象。一元函数对象。

• _Left
  二进制函数对象第一个参数将绑定的值。

返回值

产生的二进制对象绑定函数的第一个参数为 _Left.值的一元函数对象

备注

函数绑定器是一个函数，返回函数对象，适配器，因为它们可用于组合函数的某些构造类型更为复杂强大的表达式。

如果 _Func 为 Operation 类型对象，c 是常数，则 bind1st (_Func，c) 与 binder1st 类构造函数 binder1st<Operation> (_Func，c) 等效并且更方便。

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： <起作用的>

命名空间: std

请参见

参考

标准模板库