Method evalDiamondMinus

engine/temporal.go:161–198

evalDiamondMinus implements the diamond-minus operator (<-). It returns true if the atom was true at SOME point in the past interval. Syntax: <-[d1, d2] p(X) means "p(X) was true at some point between d1 and d2 ago"

(
	atom ast.Atom,
	opInterval ast.Interval,
	interval *ast.Interval,
	subst unionfind.UnionFind,
)

// It returns true if the atom was true at SOME point in the past interval.
// Syntax: <-[d1, d2] p(X) means "p(X) was true at some point between d1 and d2 ago"
func (te *TemporalEvaluator) evalDiamondMinus(
	atom ast.Atom,
	opInterval ast.Interval,
	interval *ast.Interval,
	subst unionfind.UnionFind,
) ([]unionfind.UnionFind, error) {
	// Calculate the query interval based on the operator's interval
	// The interval [d1, d2] means "from d2 ago to d1 ago"
	queryInterval, err := te.resolveOperatorInterval(opInterval)
	if err != nil {
		return nil, err
	}

	var solutions []unionfind.UnionFind

	// Query facts that overlap with the query interval
	err = te.temporalStore.GetFactsDuring(atom, queryInterval, func(tf factstore.TemporalFact) error {
		// Unify the fact with the query atom
		newSubst, err := unionfind.UnifyTermsExtend(atom.Args, tf.Atom.Args, subst)
		if err != nil {
			return nil // No match, continue
		}

		// Bind interval variables if present
		if interval != nil {
			newSubst = te.bindIntervalVariables(*interval, tf.Interval, newSubst)
		}

		solutions = append(solutions, newSubst)
		return nil
	})

	if err != nil {
		return nil, err
	}

	return solutions, nil
}

// evalBoxMinus implements the box-minus operator ([-).
// It returns true if the atom was true CONTINUOUSLY throughout the past interval.