import Control.Concurrent (threadDelay)

-- Game spec
width        =  10
height       =  10
glider       =  [(4,2),(2,3),(4,3),(3,4),(4,4)]

main = life glider

-- ASCII drawing
cls          =  putStr "\ESC[2J"
goto (x,y)   =  putStr ("\ESC[" ++ show y ++ ";" ++ show x ++ "H")
seqn []      =  return()
seqn (a:as)  =  do a; seqn as
writeat p xs =  do goto p; putStr xs
showcells b  =  seqn [writeat p "O" | p <- b]

-- Cell-related
isAlive b p  =  elem p b
isEmpty b p  =  not (isAlive b p)
neighbs (x,y)=  map wrap [(x-1,y-1), (x,y-1),
                                           (x+1,y-1), (x-1,y),
                                           (x+1,y)  , (x-1,y+1),
                                           (x,y+1)  , (x+1,y+1)]
liveneighbs b=  length . filter (isAlive b) . neighbs

-- Board-related
wrap (x,y)   =  (((x-1) `mod` width) + 1, ((y-1) `mod` height + 1))
survivors b  =  [p | p <- b, elem (liveneighbs b p) [2,3]]
births b     =  [p | p <- rmdups (concat (map neighbs b)), isEmpty b p, liveneighbs b p == 3]
rmdups []    =  []
rmdups (x:xs)=  x : rmdups (filter (/= x) xs)
nextgen b    =  survivors b ++ births b

-- Game-related
life b       =  do cls
                   showcells b
                   threadDelay 1000
                   life (nextgen b)