Question

class Student {
    // ...
    bool Graduate() { return m_bGraduate; }
    // ...
};

class School {
    vector<Student*> m_vecStudents;

    void DelAndNullify(Student* &pStd);
    void Fun1();
};

void School::DelAndNullify(Student* &pStd)
{
    if ( (pStd != NULL) && (pStd->Graduate()) )
    {
        delete pStd;
        pStd = NULL;
    }
}

void School::Fun1()
{
    for_each(m_vecStudents.begin(), m_vecStudents.end(), mem_fun(&School::DelAndNullify));
}

错误1错误C2064：term不评估为带有1个参数的函数C：\ Program Files \ Microsoft Visual Studio 10.0 \ VC \ include \ algorithm 22 1模拟

为什么我会收到此错误？

更新

将Student更改为pStd

更新//算法文件

template<class _InIt, class _Fn1> inline
_Fn1 _For_each(_InIt _First, _InIt _Last, _Fn1 _Func)
{
    // perform function for each element
    for (; _First != _Last; ++_First)
        _Func(*_First); // <<<<<<<< this line!
    return (_Func);
}

BTW，如果我将DelAndNullify定义为static，则以下行传递编译器

for_each(m_vecStudents.begin(), m_vecStudents.end(), ptr_fun(&School::DelAndNullify));

更新于05/09/2012

#include <string>
#include <fstream>
#include <vector>
#include <algorithm>
#include <iterator>
#include <string>
#include <iostream>
#include <iomanip>
#include <functional>
#include <boost/bind.hpp>

class Student {
public:
    Student(int id, bool bGraduate) : m_iID(id), m_bGraduate(bGraduate) {}
    bool Graduate() const { return m_bGraduate; }
private:
    int  m_iID;
    bool m_bGraduate;
};

class School {
public:
    School(int numStudent)
    {
        for (int i=0; i<numStudent; ++i)
        {
            m_vecStudents.push_back(new Student(i+1, false));
        }
    }

    ~School() 
    {   
        // deallocate the allocated student resource to prevent memory leak!
    }

    void DelAndNullify(Student* &pStd);
    void Fun1();

private:
    std::vector<Student*> m_vecStudents;

};

void School::DelAndNullify(Student* &pStd)
{
    if ( (pStd != NULL) && (!pStd->Graduate()) )
    {
        delete pStd;
        pStd = NULL;
    }
}

void School::Fun1()
{   // http://stackoverflow.com/questions/6065041/error-c2064-term-does-not-evaluate-to-a-function-taking-1-arguments
    std::for_each(m_vecStudents.begin(), m_vecStudents.end(), std::bind1st(std::mem_fun(&School::DelAndNullify), this));
    //boost::bind(&School::DelAndNullify, this, _1);
}

int main(int /*argc*/, char* /*argv*/[])
{
    School school(10);
    school.Fun1();
    return 0;
}

错误1错误C2535：'void std :: binder1st＆lt; _Fn2＆gt; :: operator（）（学生 *＆amp;）const'：已定义或声明的成员函数c：\ Program Files \ Microsoft Visual Studio 10.0 \ VC \ include \ xfunctional 299

Answer 1

std::mem_fun(&School::DelAndNullify)会返回一个带有School*和Student*的二元仿函数，但std::for_each期望一元仿函数仅使用Student*。请改用Boost。Bind：

std::for_each(
    m_vecStudents.begin(),
    m_vecStudents.end(),
    boost::bind(&School::DelAndNullify, this, _1)
);

如果你有一个足够新的编译器，那么你可以使用std::bind或std::tr1::bind而不是Boost库;或者，如果您使用的是具有C ++ 11 lambda支持的编译器，那么您可以执行以下操作，而不是使用任何bind：

std::for_each(
    m_vecStudents.begin(),
    m_vecStudents.end(),
    [this](Student*& s){ DelAndNullify(s); }
);

Answer 2

看起来mem_fun将您的成员函数转换为“静态”函数，该函数将对象作为其第一个参数，如：

static void DelAndNullfify(Student *pStudent);

但是你已经在pre-mem_fun'd函数中有了一个参数，所以你最终会得到：

static void DelAndNullfify(School *pSchool, Student* &prStudent);

这个参数太多了。

Answer 3

此

mem_fun(&School::DelAndNullify)

返回二进制函数，期待School*和Student*。

使用

bind1st(mem_fun(&School::DelAndNullify), this)

代替。

错误C2064：术语不评估为带有1个参数的函数

更新

更新//算法文件

更新于05/09/2012

3 个答案: