Struct ConstantConstraint 

pub struct ConstantConstraint { /* private fields */ }

Pins a variable to a single known value.

Created by Variable::is. The estimate is always 1, propose yields exactly the constant, and confirm retains only matching proposals. This is the simplest possible constraint and is used by the macro layer to bind attribute IDs and literal values.

Implementations

impl ConstantConstraint

pub fn new<T: ValueSchema>(variable: Variable<T>, constant: Value<T>) -> Self

Creates a constraint that binds variable to constant.

Trait Implementations

impl<'a> Constraint<'a> for ConstantConstraint

fn estimate(&self, variable: VariableId, _binding: &Binding) -> Option<usize>

Always returns Some(1) for the constrained variable.

fn propose( &self, variable: VariableId, _binding: &Binding, proposals: &mut Vec<RawValue>, )

Pushes the single constant value.

fn confirm( &self, variable: VariableId, _binding: &Binding, proposals: &mut Vec<RawValue>, )

Retains only proposals that match the constant exactly.

fn satisfied(&self, binding: &Binding) -> bool

Returns false when the variable is bound to a different value.

fn variables(&self) -> VariableSet

Returns the set of variables this constraint touches.

fn influence(&self, variable: VariableId) -> VariableSet

Returns the set of variables whose estimates may change when variable is bound or unbound.