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Iterate over array ref instead of array. (#1081)

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This revises the example to iterate over `&array` to dodge a few issues.
This commit is contained in:
Danny Yoo
2023-08-15 05:50:18 -07:00
committed by GitHub
parent 52284c7d13
commit 25d4281992
1 changed files with 12 additions and 1 deletions
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13
src/exercises/day-1/for-loops.md
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@ -22,7 +22,7 @@ keyword:
fn main() { fn main() {
let array = [10, 20, 30]; let array = [10, 20, 30];
print!("Iterating over array:"); print!("Iterating over array:");
for n in array { for n in &array {
print!(" {n}"); print!(" {n}");
} }
println!(); println!();
@ -79,4 +79,15 @@ implementation.
The solution and the answer to the bonus section are available in the The solution and the answer to the bonus section are available in the
[Solution](solutions-morning.md#arrays-and-for-loops) section. [Solution](solutions-morning.md#arrays-and-for-loops) section.
The use of the reference `&array` within `for n in &array` is a subtle
preview of issues of ownership that will come later in the afternoon.
Without the `&`...
* The loop would have been one that consumes the array. This is a
change [introduced in the 2021
Edition](https://doc.rust-lang.org/edition-guide/rust-2021/IntoIterator-for-arrays.html), and ...
* since the array is also accessed in the second loop, an implicit
array copy would have occured; since `i32` is a copy type, then
`[i32; 3]` is also a copy type.
</details> </details>