6 releases

0.0.7 Oct 8, 2023
0.0.6 Jul 29, 2023
0.0.4 Jun 16, 2023
0.0.2 Apr 17, 2023

#199 in Programming languages




Regen is a language that defines languages. The regen compiler generates a parser for the language defined with the Regen language in supported general-purpose programming languages:

  • Rust
  • TypeScript (originally planned but not going to be worked on any time soon - use Rust WASM instead for now)
  • Python (maybe)
  • C++ (maybe)

Regen is suitable for small application-specific grammars, such as a custom string-interpolation function or a custom command parser. It is meant to replace parse(cmd.split(" ")) with a more robust and easy-to-use parser. It is not meant to replace full-fledged parsers for existing programming languages, as those are more optimized and have more features like error recovery and better error messages.


  • Regen defines LL (Left-to-right, Leftmost derivation) grammars.
  • Lexer/Tokenizer parses tokens with regular expressions (basically DFA)
  • Semantic annotations are built-in to the Abstract Syntax Tree.
  • The Parse Tree nodes can be hooked with custom code to directly generate application-specific objects without the need for a separate pass.
  • The generated parser API is type-safe (if the target language supports it).
  • Syntax coloring to HTML, with optional classname mappings so you can use any existing theme.


Here is the grammar of Regen, defined in Regen, and highlighted with the generated parser with a Prism.js theme.


Install the compiler

cargo install regen-lang

If you are generating for Rust, you also need to add the library

cargo add regen-lang

You can use --no-default-features if you don't need the CLI to avoid dependency on clap

Documentation on https://docs.rs/regen-lang.


~92K SLoC