Extern 函式

Rust supports generics, which lets you abstract algorithms or data structures (such as sorting or a binary tree) over the types used or stored.

/// Pick `even` or `odd` depending on the value of `n`.
fn pick<T>(n: i32, even: T, odd: T) -> T {
    if n % 2 == 0 {
        even
    } else {
        odd
    }
}

fn main() {
    println!("picked a number: {:?}", pick(97, 222, 333));
    println!("picked a tuple: {:?}", pick(28, ("dog", 1), ("cat", 2)));
}
This slide should take about 5 minutes.

  • Rust 會根據引數型別和傳回的值來推斷 T 的型別。

  • 這與 C++ 模板 (template) 類似，但 Rust 會立即對泛型函式進行部分編譯，因此函式必須適用於所有符合限制條件的型別。舉例來說，如果 n == 0，請嘗試修改 pick 以傳回 even + odd。即使只使用具有整數的 pick 建立例項，Rust 仍會將其視為無效。但 C++ 就能讓您這麼做。

  • Generic code is turned into non-generic code based on the call sites. This is a zero-cost abstraction: you get exactly the same result as if you had hand-coded the data structures without the abstraction.