# ConstDefault Trait
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A `Default`-like trait and derive macros for `const` evaluation contexts.
This crate defines the `ConstDefault` trait and implements it for
Rust primitives, prelude types, tuples and arrays. Furthermore it
provides a derive macro so that users can implement `ConstDefault`
easily for their custom types.
- 100% safe Rust
- `no_std` compatible
- Full macro hygiene
- No dependencies
## Usage
Add
```toml
[dependencies]
const-default = { version = "1.0", features = ["derive"] }
```
to your `Cargo.toml` to start using it.
## Examples
### Rust Primitives
```rust
use const_default::ConstDefault;
fn main() {
assert_eq!(<i32 as ConstDefault>::DEFAULT, 0);
assert_eq!(<Option<i32> as ConstDefault>::DEFAULT, None);
assert_eq!(<String as ConstDefault>::DEFAULT, String::new());
assert_eq!(<Vec<u8> as ConstDefault>::DEFAULT, Vec::new());
}
```
### Derive
```rust
use const_default::ConstDefault;
#[derive(ConstDefault, Debug, Default, PartialEq)]
pub struct Color {
r: u8,
g: u8,
b: u8,
}
fn main() {
assert_eq!(
<Color as ConstDefault>::DEFAULT,
Color::default(),
);
}
```