Struct Variable 

pub struct Variable<D: Domain> {
    pub domain: D,
    /* private fields */
}

A CSP variable holding its current domain and an undo log for backtracking.

Fields

domain: D

Current (working) domain – mutated during search.

Implementations

impl<D: Domain> Variable<D>

pub fn new(domain: D) -> Self

Create a new variable with the given initial domain.

pub fn prune(&mut self, val: &D::Value, depth: usize) -> bool

Record that val was pruned at depth, and remove it from the domain. Returns true if the value was actually present and removed.

pub fn restore(&mut self, depth: usize)

Restore all values pruned at the given depth.

pub fn reset(&mut self)

Reset to the original domain, clearing the undo log.

pub fn set_domain(&mut self, domain: D)

Replace the current domain entirely (used during initial propagation).

pub fn clear_log(&mut self)

Drop the undo log without touching the working domain.

Used by the restart driver to bake a post-propagation “baseline” domain in place: the reductions already applied to domain are kept, but their depth-tagged log entries are discarded so subsequent restore() calls at any search depth cannot un-prune them. This is the seam fix that stops a depth-0 backtrack from silently undoing solve_with_given’s initial AC-3.

pub fn reset_to(&mut self, domain: D)

Reset the working domain to domain and clear the undo log.

The restart driver calls this to return every variable to the shared post-initial-propagation baseline before re-descending.

pub fn restrict_to(&mut self, val: &D::Value, depth: usize)

Restrict domain to a single value, recording all other removals at depth. This is the fast path for backtracking assignment — avoids collecting domain values into a Vec just to prune them.

Delegates the actual domain mutation to Domain::restrict_to, which for BitsetDomain clears every bit but val’s in one bitwise AND (O(1)) instead of this method’s previous per-value iterate-and-remove loop (O(domain size) bit ops, on top of the Vec collect it used to allocate). This method’s own job shrinks to what only it can do: recording each removed value on the depth-keyed undo log.

Trait Implementations

impl<D: Clone + Domain> Clone for Variable<D>

where D::Value: Clone,

fn clone(&self) -> Variable<D>

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl<D: Debug + Domain> Debug for Variable<D>

where D::Value: Debug,

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

Formats the value using the given formatter.