anatman

def dsh(un, va)
(va.size - 1).downto(1) {|j| va[j] = va[0 .. j].inject(1) { |pr, it| pr * it } }
ar = un.zip va
hs = {}
ar.each {|i| hs[i[0]] = i[1] }
hs
end

yds = dsh([:yd, :ft, :in], [1, 3, 12])