小编Yak*_*kov的帖子

在VS 10中,我收到警告:

warning C4800: 'int' : forcing value to bool 'true' or 'false' (performance warning)

试图编译

int x ;
static_cast<bool>(x);

如何编写一个不会引起此警告的代码？

我有几个类,每个类使用相同的,enum但根据其要求扩展了一点.例如 :

class skirtColor{
  enum Color{
red = 1,
blue = 10,
green = 12
};
};
class dressColor {
enum Color{
red = 1,
pink,
yellow,
blue = 10,
green = 12
};
};
class pantsColor {
enum Color {
red = 1,
brown,
blue = 10,
green = 12
};
};

由于C++中没有枚举的继承,我想define用于一个共同的部分

#define COLOR\
// red color \
red = 1,\
// blue color \
blue = 10,\
//green color
green = 12,

之后,我可以在类中重用常见的颜色定义 …

我有以下代码:

std::map<size_t,Cell&> m_cellMap;

当Cell定义如下:

class Cell
    {
      public:
        Cell(int x = 0,int y = 0) : m_x(x),m_y(y) { }
      private:
        int m_x;
        int m_y;
        /// class members and methods
    };

我不能编译下面的代码:

Cell c;
m_cellMap[0] = c;

得到错误:出了error C2101: '&' on constant 什么问题？如何解决？

谢谢

我有一个带参数@id int OUTPUT 的存储过程(sql server 2012)该过程向数据库表中插入一些数据并返回受影响行的ID

SET @id=SCOPE_IDENTITY()
RETURN @id

我从SQL Server测试它,它工作正常.但是当我从C#调用它时:它确实将数据插入到表中,但返回null:

SqlParameter parm = new SqlParameter("@id", SqlDbType.Int);
parm.Size = 32;
parm.Direction = ParameterDirection.Output; // This is important!
cmd.Parameters.Add(parm);
object id = (int?)cmd.ExecuteScalar();//<-null

请指出导致这种奇怪行为的原因是什么？

我有DateTimeOffset输入参数.需要创建其他DateTimeOffset参数,其中月份比输入少2个月:

//DateTimeOffset  input;
DateTimeOffset modified = new DateTimeOffset(input.Year,
input.Month - 2, input.Day,
input.Hour, input.Minute,
input.Second, input.Millisecond,
input.Offset);

I get an exception  

年,月和日参数描述不可表示的DateTime.

怎么了？ - 月份是4. S0 4-2 = 2有效谢谢

我有按第二列排序的表 (1000000x4) 的 Spark 数据框 我需要获取第二行第 0 列和第二行第 3 列的 2 个值 我该怎么做？

根据此https://docs.cloudant.com/document.html#bulk-operations 我试图将多个文档插入我的 cloudant 数据库，但出现错误：

{
  "error": {
    "statusCode": 400,
    "name": "Error",
    "request": {
      "method": "POST",
      "headers": {
        "content-type": "application/json",
        "accept": "application/json"
      },
      "uri": "https://XXXXXX:XXXXXX@8f7fc7f0-766b-4429-b060-4ef1c01f7665-bluemix.cloudant.com/ttt/_bulk_docs",
      "body": "[{\"name\":\"Nicholas\",\"_id\":\"96f898f0-f6ff-4a9b-aac4-503992f31b01\",\"_attachments\":{},\"age\":45,\"gender\":\"male\"},{\"name\":\"Taylor\",\"_id\":\"5a049246-179f-42ad-87ac-8f080426c17c\",\"_attachments\":{},\"age\":50,\"gender\":\"male\"},{\"name\":\"Owen\",\"_id\":\"d1f61e66-7708-4da6-aa05-7cbc33b44b7e\",\"_attachments\":{},\"age\":51,\"gender\":\"male\"}]"
    },
    "description": "couch returned 400",
    "scope": "couch",
    "reason": "Request body must be a JSON object",
    "error": "bad_request",
    "stack": "Error: Request body must be a JSON object\n    at Request._callback (/nodejsAction/node_modules/cloudant-nano/lib/nano.js:247:15)\n    at Request.self.callback (/nodejsAction/node_modules/request/request.js:186:22)\n    at emitTwo (events.js:106:13)\n    at Request.emit (events.js:191:7)\n    at Request.<anonymous> (/nodejsAction/node_modules/request/request.js:1081:10)\n    at emitOne (events.js:96:13)\n    at Request.emit (events.js:188:7)\n    at IncomingMessage.<anonymous> (/nodejsAction/node_modules/request/request.js:1001:12)\n    at IncomingMessage.g (events.js:291:16)", …

我有以下.h文件

class Node
{
private :
    int m_data;
    Node* m_left;
    Node* m_right;
public:
    Node(int data) : m_data(data), m_left(nullptr), m_right(nullptr) {}
    Node* getLeft() { return m_left; }
    Node* getRight() { return m_right;  }
    int getData() { return m_data;  }
};

class Tree
{
private :
    Node * m_root;
    unsigned int m_size;
    void freeNode(Node*);
    bool insert(Node**, int );
public:
    Tree() : m_size(0) {}
    ~Tree();
    int findMaximumVericalSum();
    bool insert(int);
};

实施时，出现错误-什么地方出了问题以及如何解决

'＆'需要l值

地址运算符（＆）必须具有一个l值作为操作数。

bool Tree::insert(Node** root, int data)
{
    Node* newNode = new …

我想创建一个字符串模板,其内容的一部分最近将完成

string myTemplete = "This is a template ,which depends on {1} and {2} and {3}"

之后我有一些函数调用链,我从中收集数据

int arg1 = MyFunc1();
string arg2 = MyFunc2();
string arg3 = MyFunc3();

//需要使用arg 1for {0},arg2 for {1},arg3for 填充myTemplete{2}

我该怎么做？我构建的模板很长,并且在许多地方使用,因此不想制作类似的东西

int arg1 = MyFunc1();
string arg2 = MyFunc2();
string arg3 = MyFunc3();
string myData = string.Format("This is a template ,which depends on {1} and {2} and {3}"
,arg1, arg2, arg3);

我在 cs 文件中有以下代码（在 Visual Srudio 中编译）

#if __cplusplus
// C++ region, hide the private C# key word "private" from C++
#define private
namespace fastmapping
{
#else
// C# region, namespace and class so the C++ enum would not be the same in C#
namespace Interface
{
    public static class Example
    {
#endif
        // Common part to both C# and C++ (in C++ the private keyword is omitted by define)
        private enum GatedMode
        {
            GATED_MODE,
            NON_GATED_MODE
        };

        // other enums
    } …

我有IP地址的字符串string ip = "123.37.71.238,123.37.71.239"(这是一个例子,实际上它有大约100个地址),需要生成这串名单

我该怎么做？谢谢

问题基于以下类层次结构.

Base2* d3 = new Der3();
d3->v1();
delete d3;

输出是:

Base1
Base1
Der1
Base2
Der3
v1 Base2
~Base2

我得到一个例外.为什么？(它只会产生内存泄漏)

class Base1
{
public:
    Base1() {std::cout << "Base1" << std::endl; }
    ~Base1() {std::cout << "~Base1" << std::endl; }
    virtual void v1() { std::cout << "v1 Base1" << std::endl; }
    void v2() {std::cout << "v2 Base1" << std::endl;}
    void v3() {std::cout << "v3 Base1" << std::endl;}
};

class Base2
{
public:
    Base2() {std::cout << "Base2" << std::endl; }
    ~Base2() {std::cout << "~Base2" …