mu

Documentation: www.shyal.com/mu

mu is a small language that transpiles to Python. A file is indented blocks without colons, calls of one argument without brackets, .. ranges, x -> ... lambdas, <- push, folds (sum for x in xs: f(x)), memo for a cached function with cases, and class for a Python class. The Python it produces is plain and runs anywhere; the transpiler pastes in the source of every helper the file calls.

pip install mu-language
mu file.mu        # the Python
mu --fmt file.mu  # the file, formatted
mu-repl           # a REPL

Spec

The language is specified one version at a time: v0.1, v0.2, v0.3, v0.4, v0.5, v0.6, v0.7, v0.8, v0.9, v0.10, v0.11, v0.12.

Profiles

The language owns a few helpers (Grid, deep). The rest come from a profile: a Python file that registers a project's library with mulang.library(module, *names) and the names its run time preloads with mulang.environment(objects). A project names its profile in pyproject.toml:

[tool.mu]
profile = "mu/leetmu.py"

python -m mulang, the REPL, py2mu and the ide load it from the working directory, or from the workspace root the ide is asked about. The first profile is the LeetCode one in the leet repo, whose library is the pydsa package (not yet published).

Tools

• mulang.ide: hover, completion, go-to-definition and signature help over JSON lines, through the transpiled Python and Jedi.
• mulang.py2mu: a Python solution written as mu, in as few lines as the language allows.
• vscode/: the VS Code extension (highlighting, formatter, the ide, a debugger that steps through the mu file). Install the .vsix from the latest vscode-v* release, or link the folder into ~/.vscode/extensions and reload the window. See vscode/README.md.

Releasing

PyPI: bump version in pyproject.toml, then uv build and uv publish dist/* with UV_PUBLISH_TOKEN set (.envrc).

Editor extension: bump version in vscode/package.json and add a line to vscode/CHANGELOG.md, then tag and push:

git tag vscode-v0.1.0 && git push origin vscode-v0.1.0

The vscode workflow runs the adapter tests, packages the .vsix, checks the tag against package.json, and attaches the .vsix to a GitHub release. A pull request that touches vscode/ runs the same steps without releasing. The extension is on neither registry: the VS Code Marketplace needs a Microsoft account and Open VSX an Eclipse account, and neither would open one.

Tests

pip install -e '.[test]'
pytest

The tests also need pydsa, the leet profile's library, on the path. Two of them run only under the leet harness, whose sitecustomize preloads the names LeetCode preloads; elsewhere they skip.