Enum StateEvaluation 

pub enum StateEvaluation<const N: usize> {
    Active(f32, [f32; N]),
    Terminal(f32),
}

Represents the evaluation of a game state, usually provided by a heuristic function or a neural network (e.g., in AlphaZero/MuZero architectures).

This enum strictly binds the game’s termination status with its corresponding data, preventing the representation of invalid states (like a terminal state having future policies).

Note on Score Perspective

The score value provided here (both in Active and Terminal states) must always be expressed from the perspective of the player who just made the move that led to this state. This ensures correct backpropagation in alternating-turn games when using the engine’s score_updater logic.

Variants

Active(f32, [f32; N])

The game is ongoing. Contains the current board evaluation score and the prior probabilities (policies) for the next N possible actions.

Terminal(f32)

The game has ended. Contains only the final fixed score (e.g., 1.0 for win, -1.0 for loss).

Implementations

impl<const N: usize> StateEvaluation<N>

pub fn score(&self) -> f32

Extracts the score from the evaluation, regardless of whether the state is active or terminal.

Returns

A floating-point value (f32) representing the underlying score of this state.

Trait Implementations

impl<const N: usize> Clone for StateEvaluation<N>

fn clone(&self) -> StateEvaluation<N>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<const N: usize> Copy for StateEvaluation<N>

impl<const N: usize> Debug for StateEvaluation<N>

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

Formats the value using the given formatter.

impl<const N: usize> PartialEq for StateEvaluation<N>

fn eq(&self, other: &StateEvaluation<N>) -> 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<const N: usize> StructuralPartialEq for StateEvaluation<N>