Struct History 

pub struct History { /* private fields */ }

History primary use is for tracking repeated moves to prevent threefold repetition. It is stateful, in that functions assume the next interaction comes from the next possible move in a played game.

It contains the hashes of all previously visited positions, and the indices of positions which cannot be repeated in future positions.

Implementations

impl History

pub fn empty() -> Self

Create a new empty History.

pub fn new(game: &Game, ztable: &ZobristTable) -> Self

Create a new History from a game and a Zobrist Table.

pub fn push(&mut self, hash: HashKind, is_unrepeatable: bool)

Pushes a new position into the hash history, and updates the most recent unrepeatable index if applicable.

pub fn pop(&mut self)

Pops a position from history stack. If the popped item was the most recent unrepeatable, then replace it with the previous unrepeatable index.

pub fn contains(&self, hash: HashKind) -> bool

Returns true if the position occurs at least once in history. This is done by only checking the history from the last unrepeatable index to the most recent entry. All positions before the index cannot reoccur in the next sequence.

pub fn contains_n(&self, hash: HashKind, count: usize) -> bool

Returns true if the position occurs in history at least n times, assuming the position to check may be the next move in this game’s history.

pub fn is_threefold_repetition(&self, hash: HashKind) -> bool

Returns true if the position occurs twice in history, indicating that the given position is the second repetition (position occurs total of three times).

pub fn is_twofold_repetition(&self, hash: HashKind) -> bool

Returns true if the position occurs once in history, indicating that the given position is the first repetition (position occurs total of two times).

Trait Implementations

impl Clone for History

fn clone(&self) -> History

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for History

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

Formats the value using the given formatter.

impl PartialEq for History

fn eq(&self, other: &History) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for History

impl StructuralPartialEq for History