func (s bySymValue) Less(i, j int) bool { return s[i].v < s[j].v }

// SortSub walks through the sub-symbols for 's' and sorts them
// in place by increasing value. Return value is the new
// sub symbol for the specified outer symbol.
func (l *Loader) SortSub(s Sym) Sym {

	if s == 0 || l.sub[s] == 0 {
		return s
	}