Rust中的特征界限不满足
Rust中的特征界限不满足
提问于 2016-08-29 23:50:49
我正在尝试用Rust写一个Tic Tac Toe游戏，但是这个改变字段的函数不起作用，我不知道它有什么问题：
fn change_field(mut table: [char; 9], field: i32, player: char) -> bool {
if field > 0 && field < 10 {
if table[field - 1] == ' ' {
table[field - 1] = player;
return true;
} else {
println!("That field isn't empty!");
}
} else {
println!("That field doesn't exist!");
}
return false;
}我得到了这些错误：
src/main.rs:16:12: 16:26 error: the trait bound `[char]: std::ops::Index<i32>` is not satisfied [E0277]
src/main.rs:16 if table[field-1] == ' ' {
^~~~~~~~~~~~~~
src/main.rs:16:12: 16:26 help: run `rustc --explain E0277` to see a detailed explanation
src/main.rs:16:12: 16:26 note: slice indices are of type `usize`
src/main.rs:17:13: 17:27 error: the trait bound `[char]: std::ops::Index<i32>` is not satisfied [E0277]
src/main.rs:17 table[field-1] = player;
^~~~~~~~~~~~~~
src/main.rs:17:13: 17:27 help: run `rustc --explain E0277` to see a detailed explanation
src/main.rs:17:13: 17:27 note: slice indices are of type `usize`
src/main.rs:17:13: 17:27 error: the trait bound `[char]: std::ops::IndexMut<i32>` is not satisfied [E0277]
src/main.rs:17 table[field-1] = player;
^~~~~~~~~~~~~~在更高版本的Rust中，我得到了以下错误：
error[E0277]: the trait bound `i32: std::slice::SliceIndex<[char]>` is not satisfied
--> src/main.rs:3:12
|
3 | if table[field - 1] == ' ' {
| ^^^^^^^^^^^^^^^^ slice indices are of type `usize` or ranges of `usize`
|
= help: the trait `std::slice::SliceIndex<[char]>` is not implemented for `i32`
= note: required because of the requirements on the impl of `std::ops::Index<i32>` for `[char]`
error[E0277]: the trait bound `i32: std::slice::SliceIndex<[char]>` is not satisfied
--> src/main.rs:4:13
|
4 | table[field - 1] = player;
| ^^^^^^^^^^^^^^^^ slice indices are of type `usize` or ranges of `usize`
|
= help: the trait `std::slice::SliceIndex<[char]>` is not implemented for `i32`
= note: required because of the requirements on the impl of `std::ops::Index<i32>` for `[char]`这是我在Rust的第一个项目，所以我没有太多的经验。我也尝试将字段更改为u32。
Stack Overflow用户
回答已采纳
发布于 2016-08-29 23:54:50
在注释中给出了原因：
note: slice indices are of type `usize`slice indices are of type `usize` or ranges of `usize`您需要将i32值强制转换为usize，例如：
table[(field - 1) as usize]或者，如果在您的应用程序中有意义，可以考虑使用usize作为field变量的类型。
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原文链接：
https://stackoverflow.com/questions/39210311
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