C++ 重载函数调用运算符

01_重载函数调用运算符.cpp

#include<iostream>
using namespace std;

class Func_call{
    public:
    Func_call(){cout<<"Construction"<<endl;}
    ~Func_call(){cout<<"Destructor"<<endl;}

    //重载了函数调用运算符的类，在其调用运算符执行时，可以称作函数对象
    bool operator()(int a , int b)
    {
        cout<<"operator()"<<endl;
        return a>b;
    }
};
int main()
{
    Func_call fc /*()*/;//具名对象
    Func_call /**/ ();//匿名对象
    fc(10,20);

}

02_函数对象应用场景.cpp

#include<iostream>
#include<algorithm>
using namespace std;

class Func_call{
    public:
    Func_call(){cout<<"Construction"<<endl;}
    ~Func_call(){cout<<"Destructor"<<endl;}

    //重载了函数调用运算符的类，在其调用运算符执行时，可以称作函数对象
    bool operator()(int a , int b)
    {
        cout<<"operator()"<<endl;
        return a<b;
    }
};


int main()
{
    int m[]={34,45,312,3,21,4,3246};
    for(auto k:m)
        cout<<k<<" ";
    cout<<endl;
    sort(m,m+sizeof(m)/sizeof(m[0]),
            Func_call()
            );
    cout<<"sorted:"<<endl;
    for(auto k:m)
        cout<<k<<" ";
    cout<<endl;
}

03_sort的一种内部实现.cpp

#include<iostream>
//#include<algorithm>
using namespace std;

class Func_call{
    public:
    Func_call(){cout<<"Construction"<<endl;}
    ~Func_call(){cout<<"Destructor"<<endl;}

    //重载了函数调用运算符的类，在其调用运算符执行时，可以称作函数对象
    bool operator()(int a , int b)
    {
        cout<<"operator()"<<endl;
        return a<b;
    }
};

bool sort(int * start, int *end)
{
    int i,j;
    for(i=0;i< end- start;i++)
    {
        for(j=0;j<end-start-i-1;j++)
        {
            if(start[j]>start[j+1])
            {
                int t = start[j];
                start[j]=start[j+1];
                start[j+1] =t;
            }
        }
    }
    return true;
}
typedef bool(*COMPARE)(int ,int);

bool sort(int * start, int *end, COMPARE  compare)
{
    int i,j;
    for(i=0;i< end- start;i++)
    {
        for(j=0;j<end-start-i-1;j++)
        {
        //  if(start[j]>start[j+1])
            if(!compare(start[j],start[j+1]))
            {
                int t = start[j];
                start[j]=start[j+1];
                start[j+1] =t;
            }
        }
    }
    return true;
}

bool comp(int a,int b)
{
//  return a>b; //降序
    return a<b; //升序
}

int main()
{
    int m[]={34,45,312,3,21,4,3246};
    for(auto k:m)
        cout<<k<<" ";
    cout<<endl;
//  sort(m,m+sizeof(m)/sizeof(m[0]));
    sort(m,m+sizeof(m)/sizeof(m[0]),comp);
    cout<<"sorted:"<<endl;
    for(auto k:m)
        cout<<k<<" ";
    cout<<endl;
}