Trait thincollections::thin_sentinel::ThinSentinel
source · pub trait ThinSentinel {
// Required methods
fn thin_sentinel_zero() -> Self;
fn thin_sentinel_one() -> Self;
}Expand description
ThinMap and ThinSet require two sepcial values to denote either an empty
or a removed element. This does NOT preclude these elements from being stored
in the map/set.
ThinSentinel is already implemented for all the primitives, so if you’re just
using those, there is nothing to do.
It’s generally difficult to implement ThinSentinel if the element requires a
Drop implementation. ThinMap/ThinSet have not been tested with such keys/elements.
The real requirement for this is that Drop should be no-op for the sentinel values.
Here is an example of a custom implementation:
use thincollections::thin_set::ThinSet;
use thincollections::thin_sentinel::ThinSentinel;
#[derive(Hash, Eq, PartialEq, Debug)]
struct Color {
r: u8, g: u8, b: u8
}
impl ThinSentinel for Color {
fn thin_sentinel_zero() -> Self {
Color {r: 0, g: 0, b: 0}
}
fn thin_sentinel_one() -> Self {
Color {r : 0, g: 0, b: 1}
}
}
let mut colors = ThinSet::new();
colors.insert(Color { r: 255, g: 255, b: 255 });
colors.insert(Color { r: 255, g: 255, b: 0 });
colors.insert(Color { r: 255, g: 0, b: 255 });
colors.insert(Color { r: 0, g: 255, b: 255 });
colors.insert(Color { r: 0, g: 0, b: 0 }); // no trouble storing a sentinel!
// Use derived implementation to print the colors.
for x in &colors {
println!("{:?}", x);
}