import io

// takes a function that receives two ints, returns an int
// Func is the function type keyword, to not switch it with fn (which declares
// a function)
fn function_tester (Func func ([int, int] -> int)) -> int {
    func(2, 2)
}

fn add(int a, int b) -> int {
    a + b
}

fn main () {
    // passes the function add to function_tester
    res := function_tester(add)

    // you can also create functions and put them in variables. not putting a
    // function name on the fn block makes it return a Func instance to be put
    // in a variable
    anonymous := (fn () {})

    // anonymous has type Func ([] -> void)

    io.puts("res = {res}")
}