The Dea Programming Language.

A systems programming language, built one level at a time.

Welcome to the Dea programming language!

Dea is a systems programming language organized into levels with an explicit compiler lineage. After L0, each level has one canonical compiler implemented in the preceding level.

The design is conservative by choice: a small, precisely specified language whose semantics leave no room for undefined behavior. Operations are either well-defined or rejected - at compile time or with a named runtime error.

Tertium non datur.

Language Levels

This monorepo hosts Dea's language levels. Each level has its own compiler, runtime, standard library, and documentation in a self-contained subtree:

Level	Directory	Status
Dea/L0	l0/	Released (l0-v2.1.1), self-hosted; the current stable Dea
Dea/L1	l1/	Development release (l1-v0.1.0); compiler implemented in L0
Dea/L2	l2/	Initial independent level; canonical compiler implemented in L1

Dea/L0 is Dea's foundational level: small, UB-free, and sufficient to host its own compiler. It compiles to C99, is self-hosted through its Stage 2 compiler, and remains the stable Dea toolchain. Start at l0/README.md for the L0 overview, quickstart, and language tour.

L0 2.1.1 fixes ARC cleanup for comparison temporaries and improves AddressSanitizer test validation. See l0/docs/releases/2.1.1.md for release notes and compatibility guidance.

Dea/L1 carries post-L0 language growth: wider fixed-width integer types, float/double with an explicit floating-point contract, bitwise operators, top-level const, function pointer types, the unsafe function marker, fixed-size arrays, export manifests, and selective/aliased imports, among others. Its L0-implemented canonical compiler supports per-module generated C, compile-only .o + .l1m artifacts, verified standalone linking, and multi-compilation-unit build/run, including ordered external-library, search-path, rpath, and raw driver arguments. It uses the L0 Stage 2 compiler at build time; installed L1 use needs no L0 compiler or source checkout.

L1 0.1.0 is the current development release, with standalone packages for Linux x86_64, macOS Intel and Apple Silicon, and Windows x86_64 (UCRT64), plus matching offline HTML/PDF documentation. Download l1-v0.1.0, then follow l1/docs/user/README.md. See l1/docs/releases/0.1.0.md for release notes, l1/README.md for source development, and l1/docs/roadmap.md for future work.

Dea/L2 starts from the former L1 Stage 2 implementation. Its canonical l2c compiles .l2 programs, emits .l2m interfaces, and owns its stdlib, runtime, and support inputs. Construction requires an explicit L1 toolchain, installed by default or a development toolchain selected with L2_BOOTSTRAP_MODE=development; ordinary L2 use does not invoke it. See l2/README.md.

Stability and Evolution

Stability is defined per language level:

• Dea/L0 is stable. Its current release is 2.1.1. Language, compiler CLI, and runtime compatibility changes follow L0's semantic versioning.
• Dea/L1 is under active development. Its current development release is 0.1.0; it does not promise stable language, module-interface, or binary compatibility across future releases.
• Dea/L2 is an independent development level. Its canonical compiler is implemented in L1; it does not yet have a packaged release.

L1 and L2 development does not change L0's stable status. Future breaking changes are documented and versioned within the affected level.

Versioning and Releases

Versions are scoped to one language level, not to the project as a whole:

• l0-v2.1.1 is a release of Dea/L0. There is no "Dea 2.1.1"; a project-wide version number is intentionally not defined.
• l1-v0.1.0 is a development release of Dea/L1; its publication does not change L0's stable status.
• Release tags are level-prefixed: L0 uses l0-vX.Y.Z and l0-snapshot-*; L1 uses l1-vX.Y.Z and l1-snapshot-*.
• Pre-monorepo bare tags such as v0.9.0 and v0.9.1 remain valid historical references to early L0 development.

The full release-tag and release-line gating policy lives in MONOREPO.md. Release-specific behavior and migration guidance are recorded in l0/docs/releases/2.1.1.md and l1/docs/releases/0.1.0.md.

The Bootstrap Chain

L0 retains its Python Stage 1 and self-hosted Stage 2. L1 has one compiler implemented in L0; L2 has one compiler implemented in L1. L1/L2 have no intra-level stage selection, parity gate, or self-hosting requirement. Installed L1 operation is independent of its upstream L0 construction toolchain. L1 0.1.0 is the first published canonical L0-implemented L1 development toolchain.

The architectural rationale is recorded in docs/decisions/, starting with docs/decisions/0022-single-compiler-level-lineage.md.

Getting Started

For the L1 development release, download the package for your platform from l1-v0.1.0 and follow the prerequisites and first-run instructions in l1/docs/user/README.md.

For the stable L0 toolchain, start from a fresh clone:

make venv   # create the shared repo-local virtual environment
cd l0       # all L0 build/test/install workflows run from here

Then follow the install and quickstart instructions in l0/README.md. For Windows-specific setup, see l0/README-WINDOWS.md.

For L1 bootstrap development:

make venv
cd l1
make use-dev                  # auto-prepares the repo-local upstream L0 Stage 2 compiler
source build/dea/bin/l1-env.sh

See l1/README.md for the current L1 workflow.

Repository Layout

Directory	Description
l0/	Dea/L0 compiler, runtime, docs, and tests
l1/	Dea/L1 compiler, runtime, docs, and tests
l2/	Dea/L2 compiler, runtime, docs, and tests
editors/	Shared editor grammars, modes, indexes, and fixtures
scripts/	Shared monorepo automation and helper modules
docs/	Dea-wide and monorepo-wide stable documentation
work/	Dea-wide and monorepo-wide plans and proposals
tools/	Vendored third-party dependencies

Monorepo structure, the root maintenance Makefile, the shared uv workspace, and the release-tag policy are documented in MONOREPO.md. Shared syntax highlighting, the in-repository Tree-sitter grammar, and navigation-index setup live in editors/README.md. The Dea-wide status snapshot lives at docs/project-status.md.

Contributing

See CONTRIBUTING.md for developer workflow, setup, and validation commands, and SECURITY.md for the security policy.

License

MIT or Apache 2.0, at your option.

Third-party notices: THIRD_PARTY_NOTICES.

Author

@googlielmo a.k.a. gwz