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Data sub-languages and domain-specific languages Next, macros make it possible to define data languages that are immediately compiled into code, which means that constructs such as state machines can be implemented in a way that is both natural and efficient. [25] Binding constructs Macros can also be used to introduce new binding constructs.
This example aims to improve the readability of the X macro usage by: Prefix the name of the macro that defines the list with "FOR_". Pass name of the worker macro into the list macro. This both avoids defining an obscurely named macro (X), and alleviates the need to undefine it. Use the syntax for variadic macro arguments "..." in the worker ...
A variadic macro is a feature of some computer programming languages, especially the C preprocessor, whereby a macro may be declared to accept a varying number of arguments. Variable-argument macros were introduced in 1999 in the ISO/IEC 9899:1999 ( C99 ) revision of the C language standard, and in 2011 in ISO/IEC 14882:2011 ( C++11 ) revision ...
Due to its limitations, C and C++ language features have been added over the years to minimize the value and need for the preprocessor. Constant. For a long time, a preprocessor macro provided the preferred way to define a constant value. An alternative has always been to define a const variable, but that results in consuming runtime memory.
Macro languages may be restricted to acting on specially labeled code regions (pre-fixed with a # in the case of the C preprocessor). Alternatively, they may not, but in this case it is still often undesirable to (for instance) expand a macro embedded in a string literal , so they still need a rudimentary awareness of syntax.
In 1989, C++ 2.0 was released, followed by the updated second edition of The C++ Programming Language in 1991. [32] New features in 2.0 included multiple inheritance, abstract classes, static member functions, const member functions, and protected members. In 1990, The Annotated C++ Reference Manual was published. This work became the basis for ...
For #include guards to work properly, each guard must test and conditionally set a different preprocessor macro. Therefore, a project using #include guards must work out a coherent naming scheme for its include guards, and make sure its scheme doesn't conflict with that of any third-party headers it uses, or with the names of any globally visible macros.
Translation units define a scope, roughly file scope, and functioning similarly to module scope; in C terminology this is referred to as internal linkage, which is one of the two forms of linkage in C. Names (functions and variables) declared outside of a function block may be visible either only within a given translation unit, in which case they are said to have internal linkage – they are ...