Dear All, Another I/O question. Let us say that you are given a list of files file1.dat, file2.dat...file10.dat and so on (i.e. every file is indexed by a number and every file is a single column where every entry is a string without spaces). In the snippet below I read file1.dat, convert it to a list and then print out its length. Now, how can I iterate the process on file1.dat, file2.dat and file3.dat and store the lengths in a list? I would like to map the file reading and following operations on the list [1,2.3], but that is giving me a headache. It is relatively easy to create the file name filename="file"++(show i)++".dat" , for i=1,2,3 but it the the iteration part that is giving me troubles. Any suggestion is appreciated. Cheers Lorenzo -- ##################################################################### import Data.Ord import Data.List main :: IO () main = do list_t <- readFile "file1.dat" let list = lines list_t let b = length list putStrLn "length of list is, " print b