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Expand enum sizes example and add speaker notes

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Fabian Bornhofen 2023-01-10 17:36:16 +01:00
parent a5d31d759f
commit 8d2fb11adc
1 changed files with 12 additions and 0 deletions
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src/enums/sizes.md
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@ -19,7 +19,19 @@ enum Foo {
fn main() {
dbg_size!(Foo);
dbg_size!(bool);
dbg_size!(Option<bool>);
dbg_size!(&i32);
dbg_size!(Option<&i32>);
}
```
* See the [Rust Reference](https://doc.rust-lang.org/reference/type-layout.html).
<details>
* `Option<bool>` is another example of tight packing.
* For [some types](https://doc.rust-lang.org/std/option/#representation), Rust guarantees that `size_of::<T>()` equals `size_of::<Option<T>>()`.
* Zero-sized types allow for efficient implementation of `HashSet` using `HashMap` with `()` as the value.
</details>