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// 类型 / 函数 / 控制流 / struct / match / enum / FFI
type Point = struct { x: i32, y: i32 }

fn dist_sq(a: Point, b: Point) -> i32 {
    let dx = a.x - b.x;
    let dy = b.y - a.y;
    dx * dx + dy * dy
}

fn classify(n: i32) -> *u8 {
    match n {
        0        => "zero",
        1..10    => "single digit",
        10 | 20  => "round number",
        _        => "other",
    }
}

extern fn printf(fmt: *u8, val: i32) -> i32;

fn main_jhyy() -> i32 {
    let p = Point { x: 3, y: 4 };
    let q = Point { x: 0, y: 0 };
    printf("d² = %d\n", dist_sq(p, q));
    printf("%s\n", classify(42));
    0
}