module Main {

extern func PrintInt(x: int);
extern func PrintLine(msg: String);

func Apply(x: int, op: func(int) -> int) -> int {
    return op(x);
}

func Double(x: int) -> int {
    return x * 2;
}

func main() -> int {
    // Closure as variable
    let add: func(int, int) -> int = |a: int, b: int| -> int { return a + b; };
    let sum: int = add(3, 4);
    PrintInt(sum);
    PrintLine("");

    // Closure passed to function
    let result: int = Apply(5, |x: int| -> int { return x * 3; });
    PrintInt(result);
    PrintLine("");

    // Address of named function as function pointer
    let d: func(int) -> int = &Double;
    PrintInt(d(7));
    PrintLine("");

    return 0;
}

}