langcc can serve as a replacement for lex+yacc, but is much more powerful:

• langcc generates efficient, linear-time parsers for a much more general class of grammars than lex+yacc. Specifically, langcc implements novel extensions of canonical LR parsing (described in the companion technical report) which we believe encompass virtually all languages that are "easy to parse" for humans.
• Unlike lex+yacc, langcc is general enough for real industrial languages (Python 3.9.12, Golang 1.17.8), and its generated parsers are extremely fast (1.2x faster than the standard Golang parser, 4.3x faster than CPython's).
• langcc generates a full compiler frontend, including AST struct definitions and associated traversals, hashing, pretty-printing, and automatic integration with the generated parser (no need to sprinkle C++ code into your grammar as in lex+yacc).
• langcc provides a convenient "conflict tracing" algorithm which traces LR conflicts back to an explicit "confusing input pair", rather than the opaque shift/reduce errors of lex+yacc.
• langcc also ships with a standalone datatype compiler, datacc, which generates C++ definitions of algebraic datatypes (including sum types!) from a simple declarative spec language (data.lang).
• langcc is self-hosting: it generates its own compiler frontend from a declarative BNF spec of the "language of languages" (meta.lang).

langcc also serves as the software implementation for the following technical reports, which describe several innovations on the classic LR parsing paradigm:

• Zimmerman, Joe. Practical LR Parser Generation. arXiv, 2022.
• Zimmerman, Joe. langcc: A Next-Generation Compiler Compiler. arXiv, 2022.

langcc is a research prototype and has not yet been used extensively in production. However, we believe it is essentially stable and feature-complete, and can be used as a standalone tool to facilitate rapid exploration of new compilers and programming languages.

The build has been tested on Ubuntu 22.04 and macOS 12.5, but should also run on some other versions of Ubuntu and macOS with minor adaptations.

For Ubuntu 22.04:

./deps_ubuntu.sh
make -j8
sudo make install

For macOS 12.5 (requires Homebrew):

./deps_macos.sh
make -j8
sudo make install

And, in order to bootstrap the langcc front-end itself, subsequently run:

./bootstrap.sh

Once langcc (and its companion, datacc) have been installed, one can run various examples:

• In the examples directory, there are two examples: basic and calc. Each has its own local Makefile.
• The main build process itself compiles grammars/py.lang and grammars/go.lang, producing tests build/go_standalone_test and build/py_standalone_test. (Note: These binaries require, respectively, repositories for Golang 1.17.8 located in the directory ../go, and Python 3.9.12 located in the directory ../cpython.)
• There is the language of datatypes, grammars/data.lang, which describes the input of the additional standalone tool datacc (used by langcc to automatically generate C++ implementations of algebraic datatypes).
• Finally, there is the language of languages itself, grammars/meta.lang. This language also serves as basic documentation, as it enumerates all of its own features.

For full documentation, please see the user manual, as well as the technical report which describes the theoretical development.