Gandora

Gandora is the project for gan, a compiler for an Elixir-flavored language that produces readable Python. You write Elixir-style modules, pattern matching, pipelines, and hygienic defmacro macros; deployment is ordinary Python managed by uv with the standard .venv layout. Where Elixir reaches its host platform through :erlang atom calls, Gandora reaches Python the same way: :math.sqrt(2.0) compiles to import math plus math.sqrt(2.0) with no wrapper code.

defmodule App.Mathy do
  @moduledoc "Math helpers showing patterns and interop."

  def fact(0), do: 1
  def fact(n) when n > 0, do: n * fact(n - 1)

  def norm(xs) do
    xs
    |> sum_squares()
    |> then_sqrt()
  end

  defp sum_squares(xs) do
    :functools.reduce(fn acc, x -> acc + x * x end, xs, 0)
  end

  defp then_sqrt(x), do: :math.sqrt(x)
end

compiles to plain Python with multi-clause dispatch as a match statement, private functions as _-prefixed functions, and the interop as direct imports — no Gandora runtime is needed to execute the output.

The practical guide is the language manual (中文版). Design decisions are recorded as Gandora Enhancement Proposals in geps/:

• GEP-0000 — the proposal process and translation policy (中文)
• GEP-0001 — language identity, surface syntax, module naming, configuration, and the gan CLI (中文)
• GEP-0002 — the hygienic macro system (中文)
• GEP-0003 — Python interop (中文)
• GEP-0004 — structs (frozen dataclasses) and module attributes (中文)
• GEP-0005 — sigils (~w, ~s, ~r, and the raw embedded-Python ~python) (中文)
• GEP-0006 — publishing packages as ordinary PyPI wheels, with macros shipped as source and zero runtime (中文)
• GEP-0007 — Markdown @doc with locale variants, doctests compiled to native Python doctests, gan doc / gan test (中文)
• GEP-0008 — definition-generating macros, use/__using__, and the defattr/@on_definition attribute system (中文)
• GEP-0009 — the ~<lang> embedded-language family (~sql, ~markdown, ...) with EEx-style <%= %> splices (中文)
• GEP-0010 — the standard library (std/): Enum, String, Map, List, Keyword as an ordinary package (中文)
• GEP-0011 — multi-arity name groups and \\ default parameters (中文)

English GEPs are normative; the synchronized Chinese translations are generated with scripts/translate-gep.py (a DeepSeek-backed translator configured by .env) and human-reviewed per GEP-0000-R030.

Requirements

• Rust 1.85 or newer (to build the compiler)
• Python 3.11 or newer
• uv for Python development (optional but recommended)

Quick start

cargo build --release
export PATH="$PWD/target/release:$PATH"

gan init my-app
cd my-app
gan run src/main.gan

gan init creates a uv-compatible project: pyproject.toml owns Python metadata and dependencies, gandora.jsonc owns the compiler configuration, and sources live under src/. gan run compiles into .gandora/cache/ and executes with .venv/bin/python, uv run python, or python3 — whichever is available first.

gan check              # parse, expand, analyze; no output written
gan build              # compile every module into dist/
gan expand src/x.gan   # show a module after macro expansion
gan compile src/x.gan --out build/

The v0 surface

Modules (defmodule, one per file, path-derived names), def/defp with multi-clause pattern dispatch and when guards, defmacro with quote/unquote/unquote_splicing and default hygiene (var! escapes), atoms, strings with #{} interpolation, lists, tuples, maps, keyword lists, ranges, the |> pipe, if/unless/case/cond/with, anonymous functions and captures (&Mod.fun/1, &(&1 + 1)), destructuring =, alias/import/require, the interop forms of GEP-0003 (:module calls, pyimport, postfix expr.name(...), @decorate), and the GEP-0004 data declarations: defstruct (a frozen @dataclass with %Mod{...} literals, patterns, and %Mod{s | f: v} updates) plus module attributes (@app :flask.Flask("__main__") compiles to a module-level binding, so @decorate @app.route("/") works like hand-written Python). GEP-0005 adds sigils: ~w(a b c) word lists, ~s(...) strings, ~r/\d+/ compiled Python regexes, and ~python(sum(i*i for i in range(n))) — a raw sigil that splices one verbatim Python expression into the output, Gandora's rendering of Osiris's embedded-language sigils.

Anything outside the surface produces a diagnostic naming the construct (GEP-0001-R007) rather than a silent mistranslation. See examples/tour for a working multi-module program.

Publishing a package

A Gandora package is an ordinary PyPI wheel (GEP-0006):

gan init --package acme-text
cd acme-text            # write modules under src/acme_text/
gan build               # compiles into pkg/, emits marker + .gan sources
uv build && uv publish  # standard hatchling wheel, standard PyPI

A live example is gandora-text, installable straight from GitHub with uv add git+https://github.com/mjason/gandora-text. Consumers then use it from Gandora:

require AcmeText.Core     # macros: expanded at compile time from the
alias AcmeText.Core       #         .gan sources shipped in the wheel
Core.hello("world")       # functions: a plain `import acme_text.core`

The wheel introduces no runtime: its .py modules are self-contained, Python-only consumers can use them without knowing Gandora exists, and macro expansion leaves nothing behind at runtime. The compiler discovers installed packages by reading their gandora.toml markers from .venv — it never imports or executes package code.

Data mapping

Only false and nil are falsy (Elixir semantics); the generated code inserts explicit truthiness checks where needed.

Repository layout

• src/ — the Rust compiler (lexer, parser, expander, codegen, project, CLI in main.rs)
• docs/ — the language manual (+ docs/local/zh/ translations)
• geps/ — Gandora Enhancement Proposals (+ geps/local/zh/ translations)
• examples/tour — a runnable multi-module example
• tests/e2e.rs — end-to-end tests driving the real binary
• scripts/translate-gep.py — the GEP translation tool

cargo test             # unit + end-to-end tests

Status

v0.1.0: GEP-0001..0011 are implemented and tested — the language and CLI, hygienic macros with the full metaprogramming surface (definition-generating macros, use/__using__, defattr/ @on_definition), structs, sigils and embedded languages with <%= %> splices, wheel-based package publication, bilingual docs with native doctests, multi-arity functions with \\ defaults, and the standard library (std/, uv add "git+https://github.com/mjason/gandora#subdirectory=std"). Deferred: protocols, comprehensions, try/rescue, binaries, a formatter, an LSP.