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At the time, no standard macro system was adopted by Scheme implementations. Shortly thereafter in '87, Kohlbecker and Wand proposed a declarative pattern-based language for writing macros, which was the predecessor to the syntax-rules macro facility adopted by the R5RS standard.
A macro is a piece of code that executes at compile time and either performs textual manipulation of code to-be compiled (e.g. C++ macros) or manipulates the abstract syntax tree being produced by the compiler (e.g. Rust or Lisp macros). Textual macros are notably more independent of the syntax of the language being manipulated, as they merely ...
The first application run in such a context is a more sophisticated and powerful macro compiler, written in the machine-independent macro language. This macro compiler is applied to itself, in a bootstrap fashion, to produce a compiled and much more efficient version of itself. The advantage of this approach is that complex applications can be ...
Literate Programming by Donald Knuth is the seminal book on literate programming.. Literate programming is a programming paradigm introduced in 1984 by Donald Knuth in which a computer program is given as an explanation of how it works in a natural language, such as English, interspersed (embedded) with snippets of macros and traditional source code, from which compilable source code can be ...
Procedural macros are Rust functions that run and modify the compiler's input token stream, before any other components are compiled. They are generally more flexible than declarative macros, but are more difficult to maintain due to their complexity. [125] [126] Procedural macros come in three flavors:
The twice macro in this example takes the echo statement in the form of an abstract syntax tree as input. In this example we decided to return this syntax tree without any manipulations applied to it. But we do it twice, hence the name of the macro. The result is that the code gets rewritten by the macro to look like the following code at ...
The main reason of that is that the high-level languages used to write macro code are powerful and easy to use, considerably increasing the pool of potential virus writers, and the documents containing the macros can be disseminated rapidly and widely by E-mail. [6] Macro flaws can be spread quickly and become very destructive.