Method SInter

structure/set.go:157–192

SInter returns the intersection of multiple sets. The parameter 'keys' is a variadic parameter, meaning it can accept any number of arguments. These arguments are the keys of the sets that are to be intersected.

(keys ...string)

// it can accept any number of arguments. These arguments are the keys
// of the sets that are to be intersected.
func (s *SetStructure) SInter(keys ...string) ([]string, error) {
	// if there are no keys, then there's no intersection
	if len(keys) == 0 {
		return nil, nil
	}
	// All elements of 'first' are stored in 'mem' map because it's checked
	// against each of the subsequent sets.
	first, err := s.checkAndGetSet(keys[0], false)
	if err != nil {
		return nil, err
	}

	mem := make(map[string]struct{})
	for k := range *first {
		mem[k] = struct{}{}
	}

	var members []string
	// For each other key, we get its set and its members.
	for _, key := range keys[1:] {
		fs, err := s.checkAndGetSet(key, false)
		if err != nil {
			return nil, err
		}
		// We check if each member of the current set is in 'mem'.
		// If yes, we add it to 'members' array, and remove it from 'mem' map.
		for k := range *fs {
			if _, ok := mem[k]; ok {
				delete(mem, k)
				members = append(members, k)
			}
		}
	}

	return members, nil
}

// SDiff computes the difference between the first and subsequent sets.
// It returns keys unique to the first set and an error if applicable.