在Haskell中输出不带括号且在一定范围内的列表？

Question

I have a function that returns a list, call it fn .

If I print the list, it looks like [1,2,3,4] whereas I want it to look like 1 2 3 4 .

Also I want to output many lists over a range of n , so f 1 on the first line, f 2 on the second line, ... fn on the nth line.

I have my fn function working but cannot get the output to work for the life of me.

Current attempt:

main = do
    n <- readLn :: IO Int
    mapM_ putStrLn [f i | i <- [1..n]]

Answer 1

You can do something like

list_to_string = unwords . map show

to get the output format you want. Then instead of doing

print [1, 2, 3, 4]

you can do

putStrLn $ list_to_string $ [1, 2, 3, 4]

which should display how you want.

Edit: As for printing a range, try this:

main = do
  n <- readLn :: IO Int
  mapM_ (putStrLn . list_to_string) [ f i | i <- [1..n] ]