Shulou(Shulou.com)06/01 Report--

This article introduces the relevant knowledge of "what are the core technical knowledge points of C++". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

1. Namespace namespace

Friends who have used C++ must have heard of namespaces. Yes, it is the namespace you often see. Although most students can use namespace, only a few of them are very clear about the role of namespace.

Next, let me briefly summarize it. Namespaces were introduced into the standard C++ (ANSIC++) in 1995, so why introduce such a concept?

First tell a story: there are two students with the same name in the same class, such as A, so if the teacher calls A, it will lead to conflict. I don't know which A should say yes. At this time, in order to distinguish the two students, the teacher will give them new names, BA and CA, respectively, to avoid the problem of name conflict, in fact, the same is true on C++.

The most important role of namespaces is to avoid naming conflicts in programs.

When we give a name to a class or object in the code, we are likely to encounter the situation of the same name. Some friends may feel that their code is very familiar. How can they have the same name?

Yes, if you are the only author of this project, the possibility of the same name is indeed relatively small, but the projects we come into contact with in our work are often very large, and the project team members may involve more than a dozen people. Dozens or even hundreds of people are not equal (some open source projects, authors may be thousands of people), in this case, it is difficult to ensure that the names in the code do not conflict.

There is also a naming conflict between two separate modules, but functions or variables with the same function. When our project references both modules with the same name, the compiler does not know which module to use.

Therefore, it is very reasonable and necessary to introduce the concept of namespaces.

Figuratively speaking, namespace is like a fence in a project, circling the relevant code (classes, objects, functions, variables.), these namesapce circles are independent of each other, do not affect each other, and play on their own. The painting style is like the following:

After all that has been said, how to use namespace? Please look at the following:

# includeusing namespace std;int main () {cout

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