Trait Option
pub trait OptionOrd<Rhs, InnerRhs = Rhs> {
// Required method
fn opt_cmp(&self, rhs: Rhs) -> Option<Ordering>;
// Provided methods
fn opt_lt(&self, rhs: Rhs) -> Option<bool> { ... }
fn opt_le(&self, rhs: Rhs) -> Option<bool> { ... }
fn opt_gt(&self, rhs: Rhs) -> Option<bool> { ... }
fn opt_ge(&self, rhs: Rhs) -> Option<bool> { ... }
}Expand description
Trait for values and Options that can be compared for a sort-order.
This implementation is mainly intended at working around the PartialOrd
implementation for Option, which compares Options
depending on the order of declaration in the enum.
§PartialOrd implementation for Option
let some_0 = Some(0);
let none: Option<u64> = None;
assert_eq!(none.partial_cmp(&some_0), Some(Ordering::Less));
assert_eq!(some_0.partial_cmp(&none), Some(Ordering::Greater));§Alternative behavior
In some cases, we might consider that None reflects a value which
is not defined and thus can not be compared with Some(_).
assert_eq!(none.opt_cmp(&some_0), None);
assert_eq!(some_0.opt_cmp(&none), None);§Implementations
Implementing this type leads to the following auto-implementations:
OptionOrd<Option<InnerRhs>> for T.OptionOrd<Rhs> for Option<T>.OptionOrd<Option<InnerRhs>> for Option<T>.- … and some variants with references.
This trait is auto-implemented for OptionOperations types
implementing PartialOrd<Rhs>.
Required Methods§
Provided Methods§
fn opt_lt(&self, rhs: Rhs) -> Option<bool>
fn opt_lt(&self, rhs: Rhs) -> Option<bool>
Tests whether self is less than rhs.
Returns None if they can’t be compared, e.g. if
at most one argument is None.
fn opt_le(&self, rhs: Rhs) -> Option<bool>
fn opt_le(&self, rhs: Rhs) -> Option<bool>
Tests whether self is less or equal to rhs.
Returns None if they can’t be compared, e.g. if
at most one argument is None.