Question

我正在尝试创建一个具有递归二元运算符的类从向量中获取输入但由于某种原因我一直有这些错误：

||=== Build file: "no target" in "no project" (compiler: unknown) ===|
In member function 'int ReduceGeneric::reduce(std::vector<int>&, std::vector<int>::iterator)':|
|14|error: no matching function for call to 'ReduceGeneric::binaryOperator(std::vector<int>::iterator, int&)'|
|14|note: candidate is:|
|8|note: virtual int ReduceGeneric::binaryOperator(int, int)|
|8|note:   no known conversion for argument 1 from 'std::vector<int>::iterator {aka __gnu_cxx::__normal_iterator<int*, std::vector<int> >}' to 'int'|
|16|error: invalid cast to abstract class type 'ReduceGeneric'|
|4|note:   because the following virtual functions are pure within 'ReduceGeneric':|
|8|note:     virtual int ReduceGeneric::binaryOperator(int, int)|
|22|error: invalid cast to abstract class type 'ReduceGeneric'|
||=== Build failed: 3 error(s), 0 warning(s) (0 minute(s), 0 second(s)) ===|

这是代码：

#include <iostream>
#include <vector>

class ReduceGeneric {
public:
    int reduce(std::vector<int>& v, std::vector<int>::iterator i); //set i=v.begin() in main
private:
    virtual int binaryOperator(int m, int n) =0;
    int result;
};

int ReduceGeneric::reduce(std::vector<int>& v, std::vector<int>::iterator i)   {
    if (i==v.begin())   {
        result=binaryOperator(v.begin(),*i);
        i++;
        return ReduceGeneric(v,i);
    } else if (i==v.end()) {
        return result;
    }   else    {
        result=binaryOperator(result,*i);
        i++;
        return ReduceGeneric(v,i);
    }
}

class ReduceMinimum : public ReduceGeneric  {
private:
    int binaryOperator(int m, int n);
};

int ReduceMinimum::binaryOperator(int i, int j) {
    if (i<=j)   {
        return i;
    }   else    {
        return j;
    }
}

非常感谢。我是编程的新手，所以任何输入都是一个很好的输入。显然，我的帖子充满了代码，所以我试图添加更多文本。我喜欢披萨。

Answer 1

您需要更改这些行才能成功构建：

result=binaryOperator(v.begin(),*i);

到

result=binaryOperator(*v.begin(),*i);

正如@o_weisman所说。

两行：

return ReduceGeneric(v,i);

到

return ReduceGeneric::reduce(v,i);

因为你需要调用函数而不是类。

使用int vector元素作为输入的递归方法的类

1 个答案: