1

我正在尝试制作一个可以采用任何接受[]运算符的类的函数。我希望它能够接受：

  1. 按引用或按值的数组

  2. 向量或任何其他可以索引的容器

通过一些实验，我发现我还需要一些其他特征，例如PartialOrd, PartialEq。我还需要找出容器中有多少对象。

这是我的代码：

use std::ops::Index;
use std::iter::ExactSizeIterator;
use std::cmp::PartialEq;

pub fn find<'a, I>(input: I, key: <I as std::ops::Index<u32>>::Output) -> Option<u32>
where
    I: Index<u32> + ExactSizeIterator,
    <I as std::ops::Index<u32>>::Output: PartialEq + std::marker::Sized + std::cmp::PartialOrd,
{
    if input.len() == 0 {
        return None;
    }
    if key < input[0] || key > input[(input.len() - 1) as u32] {
        return None;
    }
    let mut index: u32 = (input.len() - 1) as u32;
    loop {
        if key < input[index] {
            index /= 2;
            continue;
        } else if input[index] < key && input[index + 1] > key {
            return None;
        } else if key > input[index] {
            index += index / 2;
            continue;
        } else if input[index] == key {
            return Some(index);
        } else {
            return None;
        }
    }
}

fn main() {
    assert_eq!(find(&[1, 2], 2), Some(1));
    assert_eq!(find([1, 2], 2), Some(1));
    assert_eq!(find(vec![1, 2], 2), Some(1));
}

它会产生以下错误：

error[E0277]: the trait bound `&[{integer}; 2]: std::ops::Index<u32>` is not satisfied
  --> src/main.rs:36:16
   |
36 |     assert_eq!(find(&[1, 2], 2), Some(1));
   |                ^^^^ the type `&[{integer}; 2]` cannot be indexed by `u32`
   |
   = help: the trait `std::ops::Index<u32>` is not implemented for `&[{integer}; 2]`
   = note: required by `find`

error[E0277]: the trait bound `&[{integer}; 2]: std::iter::ExactSizeIterator` is not satisfied
  --> src/main.rs:36:16
   |
36 |     assert_eq!(find(&[1, 2], 2), Some(1));
   |                ^^^^ the trait `std::iter::ExactSizeIterator` is not implemented for `&[{integer}; 2]`
   |
   = note: required by `find`

error[E0277]: the trait bound `[{integer}; 2]: std::ops::Index<u32>` is not satisfied
  --> src/main.rs:37:16
   |
37 |     assert_eq!(find([1, 2], 2), Some(1));
   |                ^^^^ the type `[{integer}; 2]` cannot be indexed by `u32`
   |
   = help: the trait `std::ops::Index<u32>` is not implemented for `[{integer}; 2]`
   = note: required by `find`

error[E0277]: the trait bound `[{integer}; 2]: std::iter::ExactSizeIterator` is not satisfied
  --> src/main.rs:37:16
   |
37 |     assert_eq!(find([1, 2], 2), Some(1));
   |                ^^^^ the trait `std::iter::ExactSizeIterator` is not implemented for `[{integer}; 2]`
   |
   = note: required by `find`

error[E0277]: the trait bound `std::vec::Vec<{integer}>: std::ops::Index<u32>` is not satisfied
  --> src/main.rs:38:16
   |
38 |     assert_eq!(find(vec![1, 2], 2), Some(1));
   |                ^^^^ the type `std::vec::Vec<{integer}>` cannot be indexed by `u32`
   |
   = help: the trait `std::ops::Index<u32>` is not implemented for `std::vec::Vec<{integer}>`
   = note: required by `find`

error[E0277]: the trait bound `std::vec::Vec<{integer}>: std::iter::ExactSizeIterator` is not satisfied
  --> src/main.rs:38:16
   |
38 |     assert_eq!(find(vec![1, 2], 2), Some(1));
   |                ^^^^ the trait `std::iter::ExactSizeIterator` is not implemented for `std::vec::Vec<{integer}>`
   |
   = note: required by `find`
4

1 回答 1

1

我找到了一种实现它的方法，但有一些限制。

pub struct Validator {
    data: Vec<i32>,
}
impl<'a> From<&'a [i32; 2]> for Validator {
    fn from(input: &'a [i32; 2]) -> Self {
        Validator {
            data: input.iter().map(|c| *c).collect(),
        }
    }
}
impl From<[i32; 2]> for Validator {
    fn from(input: [i32; 2]) -> Self {
        Validator {
            data: input.iter().map(|c| *c).collect(),
        }
    }
}
impl From<Vec<i32>> for Validator {
    fn from(input: Vec<i32>) -> Self {
        Validator { data: input }
    }
}

pub fn find<T>(input: T, key: i32) -> Option<usize>
where
    T: std::convert::Into<Validator>,
    Validator: std::convert::From<T>,
{
    let input: Vec<i32> = input.into().data;

    if input.len() == 0 {
        return None;
    }
    if key < input[0] || key > input[(input.len() - 1)] {
        return None;
    }
    let mut index = input.len() - 1;
    loop {
        if key < input[index] {
            index /= 2;
            continue;
        } else if input[index] < key && input[index + 1] > key {
            return None;
        } else if key > input[index] {
            index += index / 2;
            continue;
        } else if input[index] == key {
            return Some(index);
        } else {
            return None;
        }
    }
}

fn main() {
    assert_eq!(find(&[1, 2], 2), Some(1));
    assert_eq!(find([1, 2], 2), Some(1));
    assert_eq!(find(vec![1, 2], 2), Some(1));
}

如果您需要一个接受 3 个或更多数字的数组的函数，则必须为每个元素数量实现它。您可以通过实现验证器结构的特征和您想要支持的类型来添加对更多结构（如VecDeque或自定义结构）的支持。Into

于 2017-12-22T18:02:59.580 回答