Haskell: rotating image 90 -

i've created image using lists of type string. kind of

pic 1 =   ["xxxx",     "x   ",     "xxx ",    "x   ",    "xxxx"] 

so i'm trying create 90 degrees rotation (clockwise). code have far, seems work level not on images.

rotateline90 :: pic -> int -> [char]      rotateline90 pic n = reverse [line!!n | line<-pic]  rotate90 :: pic -> pic   rotate90 pic = [rotateline90 pic | i<-[0 .. (length pic) - 1]] 

any ideas on how improve code.

this works

rotate90 = (map reverse .) $ foldr (zipwith (:)) $ repeat "" 

usage:

> rotate90 ["xxxx", "x   ", "xxx ", "x   ", "xxxx"] ["xxxxx","x x x","x x x","x   x"]