标签: operator-keyword

我正在使用c ++ STL堆算法,我在它周围写了一个包装类,所以我可以做一些其他的东西.当我尝试使用下面的代码时,例如:

//! Min-heap wrapper class.
class FMMHeap{
public:
    FMMHeap(Vector &phi) : _phi(phi) {}
    bool operator()(unsigned p1, unsigned p2) {return fabs(_phi(p1)) > fabs(_phi(p2)); }
    inline void pop(){ pop_heap(_heap.begin(),_heap.end(),*this); _heap.pop_back(); }
    [...lots of other stuff...]
    vectorU32 _heap;
    Vector &_phi;
}

它比我有一个像这样的单独的函数对象慢得多:

struct HeapSort{
public:
    HeapSort(Vector &phi) : _phi(phi) {}
    bool operator()(unsigned p1, unsigned p2) {return fabs(_phi(p1)) > fabs(_phi(p2)); }
private:
    Vector &_phi;
};

class FMMHeap{
public:
    FMMHeap(Vector &phi) : cmp(phi) {}
    inline void pop(){ pop_heap(_heap.begin(),_heap.end(),cmp); _heap.pop_back(); }
    [...lots of other …

作为练习我正在制作模板Array类,我想执行此操作:

Array<int> a[5];

a[4] = 2;

我怎么写这样的东西？
我试过了:

template<class T> class Array{
...
T operator[(const int loc)]=(const T temp);

这是我用C++编写的源文件.

#include<string>
#include<sstream>
#include "Lecture.hpp"
#include <iostream>

using namespace std;


Lecture::Lecture() {
  capacity=5;
  log = new int[capacity];
  used = 0;
}

/*
 * The following is copy constructor.
 */
Lecture::Lecture(Lecture& orig) {
   copy(&orig);

}

/*
 * This is an empty destructor
 */
Lecture::~Lecture() {
    // dereference dynamic memory
}

 Lecture & Lecture:: operator=(Lecture & other){
     this->copy(&other);
     return *this;
 }
 /*
  * Copy method.
  */
 void Lecture::copy(Lecture &other){    
     if(&other != this){
         capacity = other.capacity;
         log = new int[capacity];
         used = other.used; …

我有

public abstract class DataClass
{
    public static bool operator ==(DataClass left, DataClass right)
    {
        return left.Equals(right);
    }
}

这就是发生的事情

object left = new DataClass();
object right = new DataClass();
bool expected = true;
bool actual;
actual = ((DataClass)left) == ((DataClass)right);
Assert.AreEqual(expected, actual); // passes
actual = left == right;
Assert.AreEqual(expected, actual); // fails

如何让它调用正确的实现,而不是显式地强制它？

std :: array即将获得

no match for ‘operator=’ in ‘myarr = {1, 5, 2, 3, 4}’

编译此代码时出错

#include <iostream>
#include <array>

using namespace std;

int main(int argc, char const *argv[])
{
    array<int, 5> myarr;
    myarr = {1,5,2,3,4};

    for(auto i : myarr)
    {
        cout << i << endl;
    }

    return 0;
}

但是当我在同一条线上进行编译时它会编译

array<int, 5> myarr = {1,5,2,3,4};

如何在分隔线上分配值

我需要在类构造函数中赋值,我该怎么办？

class myclass
{
  myclass()
  {
    myarr = {1,2,3,4,5}; /// how to assign it   // it gives errors
  }
};

I tried to overload the operator !=

    struct Antichoc 
    { 
        quint8 Chariot; 
        quint8 Frittage;

    bool operator!=(const Antichoc &a, const Antichoc &b) 
    { 
        return a.Chariot != b.Chariot || a.Frittage != b.Frittage; 
    }
    }

我收到错误:

bool Antichoc :: operator!=(const Antichoc&,const Antichoc&)必须只有一个参数

为什么这个错误

似乎golang没有C和C ++拥有的指针运算符->。现在让我们说我有一个类似如下的函数：myfun（myparam * MyType），在函数内部，如果要访问MyType的成员变量，则必须执行（* myparam）.MyMemberVariable。在C和C ++中执行myparam-> MyMemberVariable似乎容易得多。

我很新。不确定我是否缺少某些东西，否则这不是正确的方法吗？

谢谢。

当我运行这个脚本时:

#!/bin/bash

if [[ "abcd" =~ ^.*$ ]]; then
    echo "something"
fi

我明白了:

./tmp2.sh: line 3: conditional binary operator expected
./tmp2.sh: line 3: syntax error near `=~'
./tmp2.sh: line 3: `if [[ "abcd" =~ ^.*$ ]]; then'

我已经尝试了我找到的所有建议,但仍然是一样的:/请帮助我!

我有以下列表:

languages =["java", "haskell", "Go", "Python"]
animals = ["pigeon", "python", "shark"]
names = ["Johan","Frank", "Sarah"]

我想知道以下所有三个列表中是否存在python.以下if语句是我使用"in"方法和"and"运算符得出的结果.

if("Python" in languages and "Python" in animals and "Python" in names )

有没有办法将这个语句压缩成较小的长度？
IE

if("Python" in languages and in animals and in names)

虽然我不知道你不能operator[]在C++中重载以接受多个参数,但我偶然发现了一个似乎对我有意义的声明:

#include <vector>
#include <iostream>

int main()
{
    std::vector<int> numbers{1, 2, 3, 4};

    int i = 0;
    std::cout << numbers[i++,i+=1,i=1,i+1] << std::endl;
    return 0;
}

那么有人可以解释是否有任何传递多个表达式的好处operator[]？

用mingw g ++ 4.8.1编译,带-std = c ++ 11