/// A simple function to be used as a function pointer.
fn add(a: i32, b: i32) -> i32 {
    return a + b;
}

/// Applies a binary operation to two values.
fn apply(op: fn(i32, i32) -> i32, x: i32, y: i32) -> i32 {
    return op(x, y);
}

/// Passes a function pointer to another function.
fn passPtr(x: i32, y: i32) -> i32 {
    return apply(add, x, y);
}