Method implies

index/regexp.go:174–196

implies reports whether q implies r. It is okay for it to return false negatives.

(r *Query)

// implies reports whether q implies r.
// It is okay for it to return false negatives.
func (q *Query) implies(r *Query) bool {
	if q.Op == QNone || r.Op == QAll {
		// False implies everything.
		// Everything implies True.
		return true
	}
	if q.Op == QAll || r.Op == QNone {
		// True implies nothing.
		// Nothing implies False.
		return false
	}

	if q.Op == QAnd || (q.Op == QOr && len(q.Trigram) == 1 && len(q.Sub) == 0) {
		return trigramsImply(q.Trigram, r)
	}

	if q.Op == QOr && r.Op == QOr &&
		len(q.Trigram) > 0 && len(q.Sub) == 0 &&
		stringSet.isSubsetOf(q.Trigram, r.Trigram) {
		return true
	}
	return false
}

func trigramsImply(t []string, q *Query) bool {
	switch q.Op {