N queens problem

This is the problem to figure out the n queens problem but I didn't understand it very well. Somebody can help me ? how legal and queens functions work? attack (l,c) (ll,cc) = l ==ll || (l+c==ll+cc) || (l-c==ll-cc) legal p m = and [not (attack (l,c) (m, length p +1)) | (l,c) <- zip p [1..]] queens n = r n n where r 0 n = [[]] r m n = [p ++ [m] | p <- r (m-1) n, m <-[1..n], legal p m] _________________________________________________________________ Chat with friends online, try MSN Messenger: http://messenger.msn.com