macro_rules! const_cmp {
($left:expr, $right:expr $(,)*) => { ... };
}
Expand description
Compares two values for ordering.
The arguments must implement the ConstCmp
trait.
Non-standard library types must define a const_cmp
method taking a reference.
§Limitations
The arguments must be concrete types, and have a fully inferred type. eg: if you pass an integer literal it must have a suffix to indicate its type.
§Example
use konst::{const_cmp, impl_cmp, try_equal};
use std::cmp::Ordering;
struct Fields<'a> {
foo: u32,
bar: Option<bool>,
baz: Ordering,
qux: &'a str,
}
impl_cmp!{
impl['a] Fields<'a>;
pub const fn const_cmp(&self, other: &Self) -> Ordering {
try_equal!(const_cmp!(self.foo, other.foo));
try_equal!(const_cmp!(self.bar, other.bar));
try_equal!(const_cmp!(self.baz, other.baz));
try_equal!(const_cmp!(self.qux, other.qux))
}
}
const _: () = {
let foo = Fields {
foo: 10,
bar: None,
baz: Ordering::Less,
qux: "hello",
};
let bar = Fields {
foo: 99,
bar: Some(true),
baz: Ordering::Greater,
qux: "world",
};
assert!(matches!(const_cmp!(foo, foo), Ordering::Equal));
assert!(matches!(const_cmp!(foo, bar), Ordering::Less));
assert!(matches!(const_cmp!(bar, foo), Ordering::Greater));
assert!(matches!(const_cmp!(bar, bar), Ordering::Equal));
};