泛型函数

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

  1. /// Pick `even` or `odd` depending on the value of `n`.
  2. fn pick<T>(n: i32, even: T, odd: T) -> T {
  3.     if n % 2 == 0 {
  4.         even
  5.     } else {
  6.         odd
  7.     }
  8. }
  10. fn main() {
  11.     println!("picked a number: {:?}", pick(97, 222, 333));
  12.     println!("picked a tuple: {:?}", pick(28, ("dog", 1), ("cat", 2)));
  13. }

This slide should take about 5 minutes.

  • Rust 会根据参数类型和返回值推理出 T 的类型。

  • 这与 C++ 模板类似，但 Rust 会立即编译部分通用函数，因此该函数必须对所有符合约束条件的类型都有效。例如，请尝试修改 pick 函数，如果 n == 0，则返回 even + odd。即使仅使用带有整数的“pick”实例化，Rust 仍会将其视为无效。C++ 可让您做到这一点。

  • 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.