Fibonacci & Functions

Source: crates/core/crush-lang/tests/fixtures/fibonacci.crush

The canonical recursion example — also validates type-hinted function signatures.

fn fib(n: Int) -> Int {
    if n <= 1 {
        return n
    }
    return fib(n - 1) + fib(n - 2)
}

fn main() {
    let result = fib(10)
    return result
}

What this shows:

• fn name(param: Type) -> ReturnType — typed function signature
• Recursive calls work without any special annotation
• return is explicit; there is no implicit last-expression return

A simpler function that doubles its argument (from function_call.crush):

fn double(n: Int) {
    return n * 2
}

double(21)

Functions without a -> Type annotation implicitly return Void.