std :: binary_function - 没有匹配的调用? [英] std::binary_function - no match for call?
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问题描述
#include <iostream>
#include <functional>
using namespace std;
int main() {
binary_function<double, double, double> operations[] = {
plus<double>(), minus<double>(), multiplies<double>(), divides<double>()
};
double a, b;
int choice;
cout << "Enter two numbers" << endl;
cin >> a >> b;
cout << "Enter opcode: 0-Add 1-Subtract 2-Multiply 3-Divide" << endl;
cin >> choice;
cout << operations[choice](a, b) << endl;
}
,我得到的错误是:
Calcy.cpp: In function ‘int main()’:
Calcy.cpp:17: error: no match for call to ‘(std::binary_function<double, double, double>) (double&, double&)’
为什么我得到这个错误和如何摆脱它?
Can anyone explain why I am getting this error and how to get rid of it?
推荐答案
std :: binary_function
只包含参数和返回类型的typedef。它从来不打算作为一个多态基类(即使是,你仍然有问题切片)。
std::binary_function
only contains typedefs for argument and return types. It was never intended to act as a polymorphic base class (and even if it was, you'd still have problems with slicing).
作为一种替代,你可以使用 boost :: function
(或 std :: tr1 :: function
)像这样:
As an alternative, you can use boost::function
(or std::tr1::function
) like this:
boost::function<double(double, double)> operations[] = {
plus<double>(), minus<double>(), multiplies<double>(), divides<double>()
};
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