有點難記
寫在blogger方便記憶好了
seed :: pair of integer
fst seed = decimal number
snd seed = length of gray code
graycode = unfoldr g p
p = (==0) ◦ snd
g = (div ◦ (id × (2^) ◦ (-1)) × (flip (-) ◦ ((+1) × (2^)) × (-1) ◦ snd) ◦ dup) ◦ dup
dup x = (x,x)
實在是長到有點令人厭煩XD
接下來是 unfoldl
