Method evalBoxMinus

engine/temporal.go:203–243

evalBoxMinus implements the box-minus operator ([-). It returns true if the atom was true CONTINUOUSLY throughout the past interval. Syntax: [-[d1, d2] p(X) means "p(X) was true for the entire period from d2 ago to d1 ago"

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

// It returns true if the atom was true CONTINUOUSLY throughout the past interval.
// Syntax: [-[d1, d2] p(X) means "p(X) was true for the entire period from d2 ago to d1 ago"
func (te *TemporalEvaluator) evalBoxMinus(
	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
	queryInterval, err := te.resolveOperatorInterval(opInterval)
	if err != nil {
		return nil, err
	}

	var solutions []unionfind.UnionFind

	// Query all facts matching the atom
	err = te.temporalStore.GetAllFacts(atom, func(tf factstore.TemporalFact) error {
		// Unify first to check if this fact matches
		newSubst, err := unionfind.UnifyTermsExtend(atom.Args, tf.Atom.Args, subst)
		if err != nil {
			return nil // No match, continue
		}

		// For box-minus, the fact's interval must CONTAIN the query interval
		// (the fact must be true throughout the entire query period)
		if te.intervalContains(tf.Interval, queryInterval) {
			// 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
}

// resolveOperatorInterval converts an operator interval (with durations) to absolute timestamps.
// For past operators, durations are interpreted as offsets from the evaluation time.