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February 5, 2019 13:21
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multi level sort in rust
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/// Multi-level sort a slice of Foobars according to [(field, reverse)] | |
fn sort_by_names(f: &mut [Foobar], orderings: &[(Foofields, bool)]) { | |
use std::cmp::Ordering; | |
f.sort_by(|a, b| { | |
let mut cmp = Ordering::Equal; | |
for (field, reverse) in orderings { | |
if cmp != Ordering::Equal { | |
break; | |
} | |
cmp = match *field { | |
Foofields::Foo => a.foo.cmp(&b.foo), | |
Foofields::Bar => a.bar.cmp(&b.bar), | |
Foofields::Oof => a.oof.cmp(&b.oof), | |
}; | |
cmp = if *reverse { cmp.reverse() } else { cmp }; | |
} | |
cmp | |
}) | |
} | |
/// An arbitrary struct | |
#[derive(Debug)] | |
struct Foobar { | |
foo: i32, | |
bar: i32, | |
oof: &'static str, | |
} | |
/// Typesafe enumeration of fields on `Foobar` | |
enum Foofields { | |
Foo, | |
Bar, | |
Oof, | |
} | |
fn main() { | |
let mut f = vec![ | |
Foobar { | |
foo: 3, | |
bar: 1, | |
oof: "B", | |
}, | |
Foobar { | |
foo: 1, | |
bar: 2, | |
oof: "B", | |
}, | |
Foobar { | |
foo: 2, | |
bar: 2, | |
oof: "A", | |
}, | |
]; | |
// Apply sorts in reverse order. | |
sort_by_names(&mut f, &[( Foofields::Bar, false), (Foofields::Oof, false)]); | |
println!("{:?}", &f); | |
} |
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