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As a simple example, in the C programming language, this is a typical macro that is not a parameterized macro, i.e., a parameterless macro: #define PI 3.14159 This causes PI to always be replaced with 3.14159 wherever it occurs. An example of a parameterized macro, on the other hand, is this: #define pred(x) ((x)-1)
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.
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 ...
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 ...
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.
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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 ...