If we want to use cin in the standard library, we need to std::cin To simplify this work, we can do like this using namespace::name; * Headers should not include using Declarations Why? The reason is that the contents of a header are copied into the…

#include<vector> using std::vector; //Vector is a container. //It has a collection of same type objects. //****************************************************** //Defining and Initializing vectors vector<int> ivec; //Initially empty //give iv…

In order to use string type, we need to include the following code #include<string> using std::string; 1. Defining and initializing strings string s1; //Default initialization; s1 is the empty string string s2(s1); //s2 is a copy of s1. string s2 =…

for (declaration : expression) statement; /* This statement will iterate through the elements in the given expression. expression: an object of a type that represents a sequence declaration: defines the variable that we'll use to access the underlyin…

3.1 Namespace using Declarations 1.因为C++里有名字空间的定义,例如我们使用cin的时候必须写成std::cin,如果就用一次还是可以接受的,但是如果一直都这样,那就很麻烦了.所以C++使用了一个姓的关键字using. (1)第一种用法: 例如:using namespace std; 这样子的话就可以使用std名字空间下面所有的方法而不用加std::. (2)第二种用法: 例如:using std::cin; 这样子的就只能cin前面不加std::,而其他的…

What is a namespace? A namespace defines an area of code in which all identifiers are guaranteed to be unique. By default, all variables and functions are defined in the global namespace. For example, take a look at the following snippet: 1 2 3 4 5 i…

A namespace is a scope.C++ provides namespaces to prevent name conflicts.A namespace is a mechanism for expressing logical grouping. That is, if some declarations logically belong together to some criteria(准则), they can be put in a common namespace t…

6.25~ 6.27,用了3天翻了一遍<C++ Primer>. ▶书的 固有坏处 一句话: 代码比 文字描述 好看多了.————> 直接看习题部分/ 看demo就行了 看文字在描述这个情景,还要自己脑子里想象出来这段话在说什么.经常不知道其中哪句话是个啥意思.而且看着看着就走神了.——> 除非是对存疑的代码进行解说,否则用文字来导入场景,书看起来真的很没意思. ▇▇ <cpp Primer>这个文字描述 看着让人犯困! 还是找找啥一章总结/读书笔记 性质的先来看看吧!…

namespace的用法 1.什么是命名空间 通常我们学c++的时候经常看见头文件下有一句using namespace std,有什么用呢? 例如: #include<iostream> using namespace std; int main() { cout << "Hello,World!" << endl; return 0; } 如果我们去掉这句的话,程序就会报未声明变量cout和未声明变量endl. 原来std命名空间是C++中标准库…

以下是我的代码: //TaskConfigFile.h #pragma once using namespace System::Collections::Generic; using namespace System; using namespace System::IO; using namespace System::Text; ref class TaskConfigFile { public: TaskConfigFile(); TaskConfigFile(String^ str_l…