Juvix

Description

Juvix is a dependently functional programming language for writing efficient formally-verified validity predicates, which can be deployed to various distributed ledgers. Juvix addresses many issues that we have experienced while trying to write and deploy decentralised applications present in the ecosystem of smart-contracts:

• the difficulty of adequate program verification,
• the ceiling of compositional complexity,
• the illegibility of execution costs, and
• the lock-in to particular backends.

The Juvix compiler synthesises a high-level frontend syntax with support for dependent-linearly types and several other cutting-edge research ideas from programming language design and type theory. For more details, see Juvix's documentation.

Prerequisites

• Install Stack:

  • For Ubuntu : apt install stack
  • For Debian : apt install haskell-stack
  • For Arch Linux : pacman -S stack
  • For macOS : brew install haskell-stack
  • For Windows, following the instructions here.

  It is required at least 8GB RAM for stack installation.

• You might need to install the following third-party libraries.

  • libff,
  • libsecp256k1, and
  • openssl libssl.

• And run the following Nix commands:

  nix-channel --add https://nixos.org/channels/nixpkgs-unstable
  nix-channel --update
  nix-env -u

• Nix might install the following packages:

  • libff,
  • libsecp256k1, and
  • openssl libssl.

Installation

1. To install Juvix, you can download its sources using Git from the Github repository. Then, the program can be downloaded and installed with the following commands:

   $ git clone https://github.com/anoma/juvix.git
   $ cd juvix
   $ make install

   If the installation succeeds, you must be able to run the juvix command from any location. To get the complete list of commands, please run juvix --help.

   $  juvix version
   Juvix version 0.1.1.19-a2111a3
   Branch: develop
   Commit: a2111a389be0e17291f2903d1ec7d7b94bd60cf8
   Date: Mon Sep 13 13:26:18 2021 -0500
   

2. For a more experienced user, after cloning Juvix into a local directory, to build and install the binary to the local path, you can run the following make commands: make or for full optimisations (but slower compile times): make build-prod.

   For Windows users, to use the command make, please visit this link.

Examples

Writing and compiling your first .ju contract

To write Juvix programs, you can use any text editor. However, we recommend to use VSCode with the Juvix syntax highlighting package. In the following example, we will code a validity predicate using the LLVM backend.

1. Create the file vp.ju. The file content should be as follows.

mod VP where

open Prelude
open Prelude.LLVM

type account = {
  balance : nat
}

type transaction-type = {
  account-from : account,
  account-to   : account
}

type storage = {
  transaction : transaction-type,
}

sig accept-withdraws-from : key -> storage -> storage -> bool
let accept-withdraws-from key {transaction = initial} {transaction = final}
  | key == final.account-to =
    let difference = initial.account-from.balance - final.account-from.balance
    in difference < 10
  | else = false

3. Then, you can run the following commands using the LLVM backend.

• To simply type-check your code:

  $ juvix typecheck vp.ju -b llvm

• To compile your code to a LLVM .ll file, please run the following command:

  $ juvix compile vp.ju vp.ll -b llvm
  ()

More examples of Juvix programs can be found in the examples folder.

Testing

We have plenty of examples in the folder test. To test Juvix against these examples, please run the command:

$ make test

To open a REPL , you can run one the following commands:

$ make repl-lib    # REPL with the library scoped
$ make repl-exe    # REPL with the executable scoped

Known limitations

This is a software released for experimentation and research purposes only. Do not expect API stability. Expect divergence from canonical protocol implementations. No warranty is provided or implied.

Contributing

We welcome contributions to the development of Juvix. See CONTRIBUTING.md for contribution guidelines.

Community

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