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Although namespaces are used extensively in recent C++ code, most older code does not use this facility because it did not exist in early versions of the language. For example, the entire C++ Standard Library is defined within namespace std , but before standardization many components were originally in the global namespace.
These named modules were added to include all items declared in both global and std namespaces provided by the importable standard headers. Macros are not allowed to be exportable, so users have to manually include or import headers that emit macros for use. The C++ standard has reserved std and std.* as module names. [11]
In the C++ Standard Library, several algorithms use unqualified calls to swap from within the std namespace. As a result, the generic std::swap function is used if nothing else is found, but if these algorithms are used with a third-party class, Foo, found in another namespace that also contains swap(Foo&, Foo&), that overload of swap will be used.
Access to C library functions via namespace ::std and the C++≥98 header names is preferred where possible. To encourage adoption, C++98 obsoletes the C ( *.h ) header names, so it’s possible that use of C compatibility headers will cause an especially strict C++98– 20 preprocessor to raise a diagnostic of some sort.
Most of Library Fundamentals TS I, including: [29] [30] std::string_view, a read-only non-owning reference to a character sequence or string-slice [31]; std::optional, for representing optional objects, a data type that may not always be returned by a given algorithm with support for non-return
The Objective-C runtime maintains information about the argument and return types of methods. However, this information is not part of the name of the method, and can vary from class to class. Since Objective-C does not support namespaces, there is no need for the mangling of class names (that do appear as symbols in generated binaries).
In The C++ Programming Language, Bjarne Stroustrup, on the other hand, argues that the "apparently [d]raconian restriction against per-object information in allocators is not particularly serious", [3] pointing out that most allocators do not need state, and have better performance without it.
The library has undergone a number of enhancements since this early version, including the introduction of manipulators to control formatting, and templatization to allow its use with character types other than char. Standardization in 1998 saw the library moved into the std namespace, and the main header changed from <iostream.h> to <iostream ...