veralang 0.1.7

Vera: a programming language designed for LLMs, with full contracts, algebraic effects, and typed slot references

Vera

Vera is a programming language designed for large language models to write. It has mandatory contracts, algebraic effects, typed slot references instead of variable names, and a compiler that emits WebAssembly.

Full documentation, examples, and the language specification are available at veralang.dev and in the GitHub repository.

Install a released version

Vera requires Python 3.11 or later. Create a virtual environment and install the veralang distribution:

python -m venv .venv
source .venv/bin/activate
python -m pip install veralang

On Windows, activate the environment with .venv\Scripts\activate instead. For editor and agent integration through the language server, install the LSP extra:

python -m pip install "veralang[lsp]"

The distribution is named veralang, but the installed command remains vera, and Python code still imports it as import vera. Do not run pip install vera: that name belongs to an unrelated ERAV citizen-science project on PyPI. The wheel ships the compiler and the vera command only — the bundled examples, the conformance suite, and the specification live in the GitHub repository.

Install from GitHub source

The source route provides the full environment — the examples, conformance programs, and specification alongside the toolchain (the recommended setup for agents learning the language) — and remains the route for compiler development, unreleased changes, and testing the current main branch:

git clone https://github.com/aallan/vera.git
cd vera
python -m venv .venv
source .venv/bin/activate
python -m pip install -e .

Use python -m pip install -e ".[lsp]" for the language server or python -m pip install -e ".[dev]" when working on the compiler.

Try it

public fn safe_divide(@Int, @Int -> @Int)
  requires(@Int.1 != 0)
  ensures(@Int.result == @Int.0 / @Int.1)
  effects(pure)
{
  @Int.0 / @Int.1
}

public fn main(-> @Int)
  requires(true)
  ensures(@Int.result == 5)
  effects(pure)
{
  safe_divide(2, 10)
}

vera check program.vera
vera verify program.vera    # proves main returns 5 from safe_divide's contract
vera run program.vera       # prints 5

See the CLI cookbook, language reference, supported-platform policy, and issue tracker for more.