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Source code for the Mun language and runtime.
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Mun is a programming language empowering creation through iteration.


  • Ahead of time compilation - Mun is compiled ahead of time (AOT), as opposed to being interpreted or compiled just in time (JIT). By detecting errors in the code during AOT compilation, an entire class of runtime errors is eliminated. This allows developers to stay within the comfort of their IDE instead of having to switch between the IDE and target application to debug runtime errors.

  • Statically typed - Mun resolves types at compilation time instead of at runtime, resulting in immediate feedback when writing code and opening the door for powerful refactoring tools.

  • First class hot-reloading - Every aspect of Mun is designed with hot reloading in mind. Hot reloading is the process of changing code and resources of a live application, removing the need to start, stop and recompile an application whenever a function or value is changed.

  • Performance - AOT compilation combined with static typing ensure that Mun is compiled to machine code that can be natively executed on any target platform. LLVM is used for compilation and optimization, guaranteeing the best possible performance. Hot reloading does introduce a slight runtime overhead, but it can be disabled for production builds to ensure the best possible runtime performance.

  • Cross compilation - The Mun compiler is able to compile to all supported target platforms from any supported compiler platform.

  • Powerful IDE integration not implemented yet - The Mun language and compiler framework are designed to support source code queries, allowing for powerful IDE integrations such as code completion and refactoring tools.


fn main() {
    let sum = add(a, b);

    // Comments: Mun natively supports bool, float, and int
    let is_true = true;
    let var: float = 0.5;

// The order of function definitions doesn't matter
fn add(a: int, b: int): int {
    a + b


The Mun Programming Language Book

Building from Source

Installing dependencies

Make sure you have the following dependencies installed on you machine:


Install the latest stable version of Rust, e.g. using rustup.


Mun targets LLVM 7.1.0. Installing LLVM is platform dependant and as such can be a pain. The following steps are how we install LLVM on our CI runners:

  • *nix: Package managers of recent *nix distros can install binary versions of LLVM, e.g.:
    # Ubuntu 18.04
    sudo apt install llvm-7 llvm-7-* liblld-7*
  • macOS: Brew contains a binary distribution of LLVM 7.1.0. However, as it's not the latest version, it won't be added to the path. We are using llvm-sys to manage version, but another option is to export the LLVM_SYS_70_PREFIX variable, which will not clutter your PATH. To install:
    brew install llvm@7
    # Export LLVM_SYS_PREFIX to not clubber PATH
    export LLVM_SYS_PREFIX=$(brew --prefix llvm@7)
  • windows: Binary distrubutions are available for Windows on the LLVM website, but they do not contain a number of libraries that are required by Mun. To avoid having to go to the trouble of compiling LLVM yourself, we created a repository that automatically compiles the required binaries. It also contains a release that you can download and extract to your machine. Once downloaded and extracted, add the <extract_dir>/bin folder to the PATH environment variable.


cargo build --release


The Mun Runtime is licensed under either of

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