gistfile1.hs

data Estado = N | S | E | W deriving (Show, Eq)

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

paso :: (Estado, Integer) -> (Estado, Integer)
paso (e, 0) = (e, 0)
paso (N, x) 
    | even x = paso (W, 3 * (d x))
    | odd x = paso (W, dd x)
paso (S, x) 
    | even x = paso (E, 3 * (d x))
    | odd x = paso (N, du x)
paso (E, x) 
    | even x = paso (E, 3 * (d x))
    | odd x = paso (N, du x)
paso (W, x) 
    | even x = paso (N, d x)
    | odd x = paso (S, dd x)