import Std::Io::{PrintLine, PrintInt};

// @[Checked] enables borrow checking for this function.
// &T = shared reference (read-only)
// &mut T = mutable reference (exclusive)

@[Checked]
func ScaleInPlace(val: &mut int, factor: int) {
    *val = *val * factor;
}

@[Checked]
func GetValue(val: &int) -> int {
    return *val;
}

// Unchecked functions allow raw pointers without restrictions
func UncheckedSwap(a: *int, b: *int) {
    let tmp = *a;
    *a = *b;
    *b = tmp;
}

func Main() -> int {
    var x: int = 10;
    
    // &mut allows mutation
    ScaleInPlace(&x, 3);
    PrintInt(x);  // 30
    PrintLine("");
    
    // & allows reading
    let y: int = GetValue(&x);
    PrintInt(y);  // 30
    PrintLine("");
    
    // Unchecked: raw pointers work like C
    var a: int = 5;
    var b: int = 7;
    UncheckedSwap(&a, &b);
    PrintInt(a);  // 7
    PrintLine("");
    PrintInt(b);  // 5
    PrintLine("");
    
    return 0;
}