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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.
It is unusual for a macro processor in that it uses an explicit argument stack, and user functions are defined by concatenation (similar to the Forth language). [11] aa_macro 2017 aa_macro is an open-source character-stream-based text processing language written in Python. Text is processed in a left-to-right, inside-to-outside manner.
Pythran compiles a subset of Python 3 to C++ . [165] RPython can be compiled to C, and is used to build the PyPy interpreter of Python. The Python → 11l → C++ transpiler [166] compiles a subset of Python 3 to C++ . Specialized: MyHDL is a Python-based hardware description language (HDL), that converts MyHDL code to Verilog or VHDL code.
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 C and C++, the language supports a simple macro preprocessor. Source lines that should be handled by the preprocessor, such as #define and #include are referred to as preprocessor directives . Syntactic constructs similar to C's preprocessor directives, such as C# 's #if , are also typically called "directives", although in these cases there ...
For some programming languages, the rules are written in the same language as the program (compile-time reflection). This is the case with Lisp and OCaml. Some other languages rely on a fully external language to define the transformations, such as the XSLT preprocessor for XML, or its statically typed counterpart CDuce.
It is not to be confused with macros, the mechanism often found in programming languages (like C or Scala) to express substitution rules for program pieces. Macroprogramming originated in the context of wireless sensor network programming [ 3 ] [ 4 ] [ 5 ] and found renewed interest in the context of the Internet of Things [ 6 ] and swarm ...