Struct Lookahead 

pub struct Lookahead { /* private fields */ }

A cursor that runs a fixed distance ahead of a scan, handing out each item that many items before the scan consumes it, so the caller can prefetch what the item’s work reads.

Call Self::advance with the scan’s unconsumed tail before consuming its next item. It returns every item exactly once, in scan order, and the first call returns the scan’s first distance + 1 items so the pipeline starts full.

Over a scan of eight items at distance two, the call before each item returns:

before item 0   remaining [0 1 2 3 4 5 6 7]   returns [0 1 2]   (fills the window)
before item 1   remaining   [1 2 3 4 5 6 7]   returns [3]
before item 2   remaining     [2 3 4 5 6 7]   returns [4]
...
before item 5   remaining           [5 6 7]   returns [7]
before item 6   remaining             [6 7]   returns []        (the tail is spent)

Implementations

impl Lookahead

pub const fn new(distance: usize) -> Self

A cursor over one scan that runs distance items ahead.

pub fn advance<'a, T>(&mut self, remaining: &'a [T]) -> &'a [T]

The items within distance of the scan’s next item that no earlier call returned. remaining holds the scan’s unconsumed tail, in order.

Panics

Panics if remaining starts more than distance + 1 items before the first item no earlier call returned.

Trait Implementations

impl Clone for Lookahead

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Lookahead

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.