type UnitType struct {
	DefaultUnit Unit
	Units       []Unit
}

// findByAlias returns the unit associated with the specified alias. It returns
// nil if the unit with such alias is not found.
func (ut UnitType) findByAlias(alias string) *Unit {
	for _, u := range ut.Units {
		for _, a := range u.aliases {
			if alias == a {
				return &u
			}
		}
	}