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# Derive
The compiler is capable of providing basic implementations for some traits via
the `#[derive]` [attribute][attribute]. These traits can still be
manually implemented if a more complex behavior is required.
The following is a list of derivable traits:
* Comparison traits:
[`Eq`][eq], [`PartialEq`][partial-eq], [`Ord`][ord], [`PartialOrd`][partial-ord].
* [`Clone`][clone], to create `T` from `&T` via a copy.
* [`Copy`][copy], to give a type 'copy semantics' instead of 'move semantics'.
* [`Hash`][hash], to compute a hash from `&T`.
* [`Default`][default], to create an empty instance of a data type.
* [`Debug`][debug], to format a value using the `{:?}` formatter.
```rust,editable
// `Centimeters`, a tuple struct that can be compared
#[derive(PartialEq, PartialOrd)]
struct Centimeters(f64);
// `Inches`, a tuple struct that can be printed
#[derive(Debug)]
struct Inches(i32);
impl Inches {
fn to_centimeters(&self) -> Centimeters {
let &Inches(inches) = self;
Centimeters(inches as f64 * 2.54)
}
}
// `Seconds`, a tuple struct with no additional attributes
struct Seconds(i32);
fn main() {
let _one_second = Seconds(1);
// Error: `Seconds` can't be printed; it doesn't implement the `Debug` trait
//println!("One second looks like: {:?}", _one_second);
// TODO ^ Try uncommenting this line
// Error: `Seconds` can't be compared; it doesn't implement the `PartialEq` trait
//let _this_is_true = (_one_second == _one_second);
// TODO ^ Try uncommenting this line
let foot = Inches(12);
println!("One foot equals {:?}", foot);
let meter = Centimeters(100.0);
let cmp =
if foot.to_centimeters() < meter {
"smaller"
} else {
"bigger"
};
println!("One foot is {} than one meter.", cmp);
}
```
### See also:
[`derive`][derive]
[attribute]: ../attribute.md
[eq]: https://doc.rust-lang.org/std/cmp/trait.Eq.html
[partial-eq]: https://doc.rust-lang.org/std/cmp/trait.PartialEq.html
[ord]: https://doc.rust-lang.org/std/cmp/trait.Ord.html
[partial-ord]: https://doc.rust-lang.org/std/cmp/trait.PartialOrd.html
[clone]: https://doc.rust-lang.org/std/clone/trait.Clone.html
[copy]: https://doc.rust-lang.org/core/marker/trait.Copy.html
[hash]: https://doc.rust-lang.org/std/hash/trait.Hash.html
[default]: https://doc.rust-lang.org/std/default/trait.Default.html
[debug]: https://doc.rust-lang.org/std/fmt/trait.Debug.html
[derive]: https://doc.rust-lang.org/reference/attributes.html#derive
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