1 unstable release
0.1.0 | Aug 8, 2023 |
---|
#20 in #comparing
31 downloads per month
Used in 3 crates
(via pest_typed)
43KB
841 lines
cmp_by_derive
This crate provides the CmpBy
and HashBy
derive macros.
CmpBy
derives the traitsOrd
,PartialOrd
,Eq
andPartialEq
on types that can't automatically derive those traits because they contain unorderable fields such asf32
by selecting fields to use in the comparison.CmpBy
andHashBy
can also implement their traits by calling arbitrary methods
Usage
Fields that should be used for sorting are marked with the attribute #[cmp_by]
.
Other fields will be ignored.
This saves a lot of boilerplate, as you can see with the SomethingElse
struct.
use std::cmp::Ordering;
use cmp_by_derive::CmpBy;
#[derive(CmpBy)]
struct Something {
#[cmp_by]
a: u16,
#[cmp_by]
b: u16,
c: f32,
}
struct SomethingElse {
a: u16,
b: u16,
c: f32,
}
impl Eq for SomethingElse {}
impl PartialEq<Self> for SomethingElse {
fn eq(&self, other: &Self) -> bool {
self.cmp(other) == Ordering::Equal
}
}
impl PartialOrd<Self> for SomethingElse {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl Ord for SomethingElse {
fn cmp(&self, other: &Self) -> Ordering {
self.a.cmp(&other.a).then_with(|| { self.b.cmp(&other.b) })
}
}
assert_eq!(Something { a: 2, b: 0, c: 0.2 }.cmp(&Something { a: 1, b: 1, c: 1.3 }),
SomethingElse { a: 2, b: 0, c: 0.2 }.cmp(&SomethingElse { a: 1, b: 1, c: 1.3 }));
assert_eq!(Something { a: 1, b: 0, c: 3.3 }.cmp(&Something { a: 1, b: 1, c: 2.3 }),
SomethingElse { a: 1, b: 0, c: 3.3 }.cmp(&SomethingElse { a: 1, b: 1, c: 2.3 }));
You can use HashBy
the same way you would use CmpBy
:
use cmp_by_derive::HashBy;
use cmp_by_derive::CmpBy;
use std::collections::hash_set::HashSet;
#[derive(HashBy, CmpBy)]
struct Something {
#[cmp_by]
#[hash_by]
a: u16,
#[cmp_by]
#[hash_by]
b: u16,
c: f32,
}
let mut set = HashSet::new();
let something = Something { a: 2, b: 0, c: 0.2 };
assert!(set.insert(something));
Dependencies
~250–710KB
~17K SLoC