Scripts

There is no implicit main function in mimas. Unlike Rust, a script just runs top to bottom – write whatever code you like at the file’s root and execute it directly, the way you would with Python or JavaScript.

// hello.mim
print("Hello, world!"); // runs the moment you execute the file

mimas run hello.mim

Top-level statements run in order, and top-level fns, structs, and similar declarations are available throughout the file regardless of where they’re declared.

print(greet("world"));      // works -- `greet` is visible across the whole file

fn greet(name: str) -> str {
    f"hello, {name}!"
}

Projects

A project is a directory. Its scripts and modules can sit anywhere in it, subdirectories included, without any setup. mimas run script.mim will compile all the modules in that script’s project and then execute its code. mimas run ./some/dir treats the directory as the project, and can be used if it has only one script file to choose from.

mimas run my_project           # runs the one script in my_project
mimas run my_project/game.mim  # or picks one of many

A script’s project is the highest folder holding a .mim file in the cargo package or git repository around it, along with every folder below that. A script outside of both only sees the .mim files next to it. Another cargo package or a cargo target directory is never part of a project. The language server follows the same rules.

Cargo Projects

A project inside a cargo package is usually run by that package’s Rust host, which can give its scripts functions, types, and constants of its own. By default, mimas has the export-api feature enabled. With this on, the first time your host compiles scripts, it writes a manifest of everything it installed (the standard library and your host’s own items) to target/mimas/<binary_name>.json. Each binary and example writes its own, so hosts sharing a target dir don’t overwrite each other. This only happens while the host runs from inside its cargo target dir, so shipped builds never write one, and neither do tests or benches. You can turn the automatic write off with default-features = false, and you’re always free to export it yourself with mimas::write_api (such as a copy you ship for modders):

let library = mimas::Vm::new().install_library(mimas::library::std);
mimas::write_api(&library, "scripts/api.json".as_ref())?;

mimas check, mimas build and the language server find the manifest on their own, checking a project’s scripts against the newest one written by a binary of its package. Until the host has run, they warn and fall back to the standard library alone. After you change your host’s API, run it again to update the manifest. A manifest only works with the version of mimas that wrote it.