unary_function<> Structure
在 Visual C++ 演示如何使用 unary_functionAMP_LTAMP_GT 结构。
template<class _A, class _R>
struct unary_function
{
typedef _A argument_type;
typedef _R result_type;
};
备注
备注
类/参数名在原型不匹配版本在头文件。修改某些提高可读性。
使用unary_function ，以便更好地定义运算符函数的基类具有以下格式: Result_Type classname"::运算符x(Argument_Type)。
示例
// unary_function.cpp
// compile with: /EHsc
//
// Structure used:
// unary_function<int, float> - allows us
// to write operator functions accepting an
// integer and returning floats.
////////////////////////////////////////////
#include <functional>
#include <iostream>
using namespace std ;
/* derive class from unary_function in order to use it */
class unary_test : public unary_function<int,float>
{
public:
float value;
unary_test(){value=10.0;}
unary_test(float x){value=x;}
result_type operator*(argument_type x);
result_type operator-(argument_type x);
};
/* You can now easily create operators that accept */
/* an int and return a float. */
unary_test::result_type unary_test::operator*(unary_test::argument_type x)
{
float tmp = value * (float)x;
cout << "Value after * is " << tmp << endl ;
return value;
}
unary_test::result_type unary_test::operator-(unary_test::argument_type x)
{
float tmp = value - (float)x;
cout << "Value after minus is " << tmp << endl ;
return tmp;
}
int main(void)
{
unary_test item;
unary_test item2(18.0);
cout << "Begin" << endl ;
cout.setf(ios::fixed) ;
item = item * 2;
item2 = item2 - 5;
}
要求
标题: functional