Hello, World

Let's start with the simplest possible program. Create a file called hello.rue:

fn main() -> i32 {
    0
}

Every Rue program needs a main function that returns an i32. This return value becomes the program's exit code—0 means success.

Compiling and Running

Compile and run it:

RUE="$(scripts/rue-bin)"
"$RUE" hello.rue -o hello
./hello
echo $?  # prints: 0

The compiler takes the source file (hello.rue) and produces an executable (hello).

For quick experiments, you can also let the repository wrapper build the compiler, compile your file to a temporary executable, and run it:

scripts/rue exec hello.rue
echo $?  # prints: 0

Printing Output

To print user-facing text, use println:

fn main() -> i32 {
    println("Hello, Rue!");
    0
}

Run this program and you'll see:

Hello, Rue!

println writes a string followed by a newline. Use print when you do not want the trailing newline.

For quick debugging, Rue also provides the @dbg intrinsic:

fn main() -> i32 {
    @dbg(42);
    0
}

This prints the value followed by a newline:

42

The @ prefix indicates a compiler intrinsic—a built-in operation provided by the compiler. Use println for normal program output and @dbg when you want to inspect a value while developing.