Trait LexicographicComparator

pub trait LexicographicComparator: Comparator {
    // Required methods
    fn compare_elem(a: u8, b: u8) -> Ordering;
    fn successor(elem: u8) -> Option<u8>;
    fn predecessor(elem: u8) -> Option<u8>;
    fn max_elem() -> u8;
    fn min_elem() -> u8;
}

Define a lexicographic comparator, which is a special case of Comparator.

Types that implements LexicographicComparator will automatically have Comparator implemented as well, where the Comparator::compare is implemented per the definition of lexicographic ordering with LexicographicComparator::compare_elem.

This trait is introduced to support prefix iterators, which implicit assumes that the underlying key comparator is lexicographic.

Required Methods

fn compare_elem(a: u8, b: u8) -> Ordering

Compare a single byte; this function is used to implement Comparator::compare by definition of lexicographic ordering.

Safety

This function must never crash.

fn successor(elem: u8) -> Option<u8>

Advances the given elem to its immediate lexicographic successor, if possible. Returns None if elem is already at its maximum value with respect to the lexicographic order defined by this comparator.

fn predecessor(elem: u8) -> Option<u8>

Moves the given elem to its immediate lexicographic predecessor, if possible. Returns None if elem is already at its minimum value with respect to the lexicographic order defined by this comparator.

fn max_elem() -> u8

Returns the maximum byte value per the comparator’s lexicographic order.

fn min_elem() -> u8

Returns the minimum byte value per the comparator’s lexicographic order.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors