bind1st Function

會建立一個配置器轉換二進位函式物件成員的一元 (Unary) 函式物件透過繫結二進位函式的第一個引數為指定值的 Helper 函式樣板。

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

參數

• _Func
  要轉換的二進位函式物件轉換為一元的函式物件。

• _Left
  二進位函式物件的第一個引數要繫結的值。

傳回值

一元函式物件從繫結二進位函式物件的第一個引數所產生的值的 _Left.

備註

函式繫結器是一種功能，配置器，因為它們傳回函式物件，可用於函式複合的某些型別建構更複雜且更強大的運算式。

如果 _Func 是型別 Operation 物件，並 c 是常數，則 bind1st (_Func， c) 與 binder1st 類別建構函式 binder1st<Operation>相等 (_Func， c) 且更方便。

範例

// 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;
}

需求

標題: <functional>

命名空間: std

請參閱

參考

標準樣板程式庫