All identifiers at namespace scope are visible to one another without qualification. You are directing the compiler to make all of the names in the std namespace part of the global namespace, and thus they can be referred to without quali. Multiple namespace blocks with the same name are allowed. Secondly, declaring your own namespaces can help control the scope of class and method names in larger programming projects. They will now collide with any names that your own code uses. Thus, the advantage is that you wont have to type std in front of all functions of that namespace. This tutorial has been prepared for the beginners to help them.
The statement using namespace std is generally considered bad practice. Identifiers outside the namespace can access the members by using the fully qualified name for each identifier, for example std vector std string vec. The keyword using technically means, use this whenever you can. Why using namespace std is considered bad practice. However, it may happen that you have different namespaces that have functions of the same name.
A namespace is a declarative region that provides a scope to the identifiers names of the types, function, variables etc inside it. Net framework classes use namespaces to organize its many classes. Namespaces allow to group entities like classes, objects and functions under a name. For example, if the only part of the std namespace that you intend to use is cout, you can refer to it as follows. Using namespaces, we can create two variables or member functions having the same name. This means that one way to call them is by using std cout and std cin. Subsequent code can refer to cout without prepending the namespace, but other items in the std namespace will still need to be explicit as follows. All declarations within those blocks are declared in the named scope. Using using how to use the std namespace university of. If you have a bunch of namespaces that declare functions with the same signatures, then you can standardize your namespace struct for that set, and choose which namespace to use at runtime. The namespace mechanism creates a collection of classes, free functions, constant declarations and so.700 802 1524 1223 1429 522 221 36 1386 248 1106 524 1555 357 824 1022 1549 171 566 1510 756 95 902 463 689 537 1298 258 494 875 1004 490 950 703 178 1031 513 1277 1559 1283 546 413 570 732 1213 854