Miscellaneous

C++11 follows the lead of C99 in allowing for implementation-dependent extended integer types. Such types, for example, could be used on a system with 128-bit integers. Extended types are supported in the C header file stdint.h and in the C++ version, cstdint.

C++11 provides a mechanism, the literal operator, for creating user-defined literals. Using this mechanism, for instance, one can define binary literals, such as 1001001b, which the corresponding literal operator will convert to an integer value.

C++ has a debugging tool called assert. It is a macro that checks during runtime if an assertion is true and which displays a message and calls abort() if the assertion is false. The assertion would typically be about something the programmer thinks should be true at that point in the program. C++11 adds the keyword static_assert, which can be used to test assertions during compile time. The primary motivation is to make it easier to debug templates for which instantiation takes place during compile time, not runtime.

C++11 provides more support for metaprogramming, which is creating programs that create or modify other programs or even themselves. In C++ this can be done during compile time using templates.

Language Change

How does a computer language grow and evolve? after usage of C++ became sufficiently widespread, the need for an international standard became clear, and control of the language essentially passed to a standards committee—first the ANSI committee, then the joint ISO/ANSI committees, and currently to ISO/IEC JTC1/SC22/WG21 (the C++ Standards Committee). ISO is the International Organization for Standardization, IEC is the International Electrotechnical Commission, JTC1 is the Joint Technical Committee 1 of the preceding two organizations, SC22 is the JTC1 subcommittee for programming languages, and WG21 is the SC22 working group for C++.

The committee considers defect reports and proposals for changes in and extensions to the language, and it attempts to reach a consensus. This is neither a speedy nor a simple process. The Design and Evolution of C++ (Stroustrup, Addison-Wesley, 1994) provides some insight on this subject. Anyway, the possibly contentious and ponderous dynamics of a consensus-seeking committee are not the best way to encourage the blossoming of a multitude of innovations. Nor is that the proper role of a standards committee.

But with C++ there is a second avenue for change: direct action by the creative C++ programming community. Programmers can’t independently change the language, but they can create useful libraries. Well-designed libraries can extend the usefulness and versatility of the language, increase reliability, and make programming easier and more enjoyable. Libraries build on the existing features of a language, so they don’t require any additional compiler support. And if they are implemented through templates, they can be distributed as text files in the form of header files.

One example of this sort of change is the STL, primarily created by Alexander Stepanov, and made freely available by Hewlett-Packard. Its success with the programming community made it a candidate for the first ANSI/ISO standard. Indeed, its design influenced other aspects of the emerging standard.