是否可以使用泛型的类型参数来控制数组的大小? [英] Is it possible to control the size of an array using the type parameter of a generic?

问题描述

以下内容仅用作示例，并非有效的 Rust 代码.

What follows is just used as an example, and not valid Rust code.

struct Vec<T: Sized, Count> {
    a: [T; Count]
}

类似的东西在 C++ 模板中是可能的，但我没有在 Rust 中看到过.

Something like it is possible in C++ templates, but I haven't seen it in Rust.

推荐答案

Rust 1.51

使用常量泛型:

struct Vec<T: Sized, const COUNT: usize> {
    a: [T; COUNT],
}

以前的版本

RFC 2000 — const 泛型 引入了对此的支持进度在 issue #44580 中进行跟踪.

Previous versions

RFC 2000 — const generics introduces support for this and progress is tracked in issue #44580.

如果您查看 Rust 的设计，您会注意到它首先解决了最困难的问题(内存安全、无数据竞争)，但在其他方面还有很多不完整"的地方.(与可以实现的目标相比).

If you look at the design of Rust, you will notice that it started first by tackling the hardest problems (memory-safe, data-race free) but there are otherwise lots of areas where it is "incomplete" (compared to what could be achieved).

特别是，通用结构和函数开始时有些受限:

In particular, generic structures and functions started out somewhat limited:

• 缺乏更高级的类型 (HKT)
• 缺少非类型参数=>数组是特殊情况，为数组实现 trait 是一个已知问题，解决方法是针对几个不同的维度实施它
• 缺少可变参数=>元组是特殊情况，为所有元组实现一个特征同样困难

• lack of Higher Kinded Types (HKT)
• lack of non-type parameters => arrays are special-cased, and implementing a trait for an array is a known issue, the work-around being to implement it for a few different dimensions
• lack of variadic parameters => tuples are special-cased, and implementing a trait for all tuples is similarly difficult

目前，并非所有这些都已实施，不是因为不需要它们，而仅仅是因为时间不够.Rust 1.0 的想法不是发布不会进化的最终产品，而是发布一个稳定的基础；部分或全部会来.

For the moment, not all of these are implemented, not because they are not desired but simply because time was lacking. The idea of Rust 1.0 was not to release a final product that would not evolve, but a stable base from which to start; some or maybe all will come.

这篇关于是否可以使用泛型的类型参数来控制数组的大小?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！