complete

# File lib/optparse.rb, line 433
    def complete(key, icase = false, pat = nil)
      candidates = candidate(key, icase, pat, &method(:each)).sort_by {|k, v, kn| kn.size}
      if candidates.size == 1
        canon, sw, * = candidates[0]
      elsif candidates.size > 1
        canon, sw, cn = candidates.shift
        candidates.each do |k, v, kn|
          next if sw == v
          if String === cn and String === kn
            if cn.rindex(kn, 0)
              canon, sw, cn = k, v, kn
              next
            elsif kn.rindex(cn, 0)
              next
            end
          end
          throw :ambiguous, key
        end
      end
      if canon
        block_given? or return key, *sw
        yield(key, *sw)
      end
    end