Why are Injected Class Names Necessary in C ?

Injected Class Names in C : Unveiling Their Purpose

In C , an injected class name refers to the phenomenon where a class's name is injected into its own scope. This feature raises questions about its necessity and origins.

Purpose of Injected Class Names

The injected class name ensures that within the class's body, the class name always refers to the current class, even if another class with the same name is declared in the enclosing scope. Consider the following example:

void X() { }
class X {
public:
  static X create() { return X(); }
};

In the above code, the purpose of the injected class name is to distinguish between creating a temporary X object and calling the X function. At namespace scope, the create() function would call the function X, while within the class's body, the injected class name ensures that it refers to the class itself.

Significance in Class Templates

Injected class names are also useful in class templates. They allow the use of the class name without specifying a template argument list, making it easier to refer to the current instantiation. For instance, instead of using Foo, you can simply use Foo.

Introduction and Terminology

The concept of injected class names existed in C 98, but the terminology was introduced in C 03. C 98 referred to it as "inserting a class-name into the scope of the class itself." C 03 coined the term "injected-class-name."

Conclusion

Injected class names are a valuable feature in C that ensures proper name lookup within classes and simplifies syntax for class templates. Understanding their purpose and historical evolution enhances the mastery of C programming.

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