gistfile1.hs

d n = div n 2
dd n = div (n-1) 2
du n = div (n+1) 2

dosportres :: Integer -> Integer
dosportres x = (3^k) * r where
    (k,r) = descomp x

-- Reemplazar: no es tail recursive
dptdoble :: Integer -> Integer
dptdoble x = if (mod x 4 == 0) then 3 * (dptdoble (div x 4)) else x

ronda :: Integer -> Integer
ronda x
    | mod x 8 == 1 = d.dd.du $ x
    | mod x 8 == 3 = dd.(*3).d.du $ x
    | mod x 8 == 5 = dd.dd.du $ x
    | mod x 8 == 7 = dptdoble.du $ x
    | ((even k) && (mod r 4 == 1)) || 
      ((odd k) && (mod r 4 == 3)) = d.dd.dosportres $ x
    | ((odd k) && (mod r 4 == 1)) ||
      ((even k) && (mod r 4 == 3)) = dd.dd.dosportres $ x where
        (k,r) = descomp x

-- 2^k r -> k, r
descomp :: Integer -> (Integer, Integer)
descomp x = descomp' (0,x) where
    descomp' :: (Integer, Integer) -> (Integer, Integer)
    descomp' (d,r) = if even r then descomp' (d+1,div r 2) else (d,r)