macL

macL is a hypothetical programming language used in academic contexts to illustrate macro systems and metaprogramming. It is not intended for production use but serves as a teaching and research tool.

Design aims: its core feature is a hygienic macro system that allows code to generate and transform syntax during compilation without accidental variable capture. It provides first-class macro definitions, macro expansion timing at compile time, and a lightweight module system. The language balances macro power with a safety net: type inference, optional static typing, and explicit macro hygiene rules.

Syntax and semantics: macL uses a Lisp-inspired macro syntax for macros, integrated with a C-like core syntax for ordinary code. The macro expander operates during the semantic phase, expanding macro invocations into ordinary code before type checking; this helps ensure generated code adheres to language rules. Modules encapsulate macro definitions and prevent leakage across boundaries.

History and implementations: macL originated in theoretical discussions of metaprogramming and macro hygiene; several research teams published reference designs and small interpreters to demonstrate concepts. Experimental compilers exist in educational repositories and are used in seminars and coursework. The status is research-oriented rather than industrially adopted.

Use cases and influence: macL is used to study macro hygiene, DSL embedding, and code generation techniques. It informs discussions in macro systems for other languages, and contributions typically focus on safe syntax transformation, analyzability of macro-expanded code, and tooling support such as debuggers and editors.