Your first program

Create hello.vow:

fn main(caps: Caps) -> int {
    return 1 + 2;
}

Every program’s entry point is fn main(caps: Caps) -> int. Capabilities enter only here. If you never use caps, you still must declare it.

Build and run

vow build hello.vow -o hello
./hello
echo $?   # 3

Or:

vow run hello.vow

fn unwrap_or(opt: Option<int>, fallback: int) -> int {
    return match opt {
        Some(x) => x,
        None => fallback
    };
}