Haskell字符串的int元组列表

Question

I'm trying to write out my list of tuples from:

[(8,7),(5,6),(3,3),(9,4),(5,4)]

to:

8 7 5 6 3 3 9 4 5 4

this is how far i've come: (Updated)

showTuples :: Board -> String
showTuples = unwords . fmap show . concatMap (\(x,y) -> [x,y])

I know i'm suppose to map this function to all elements of my list but i can't seem to get it right.

(UPDATE) It worked, still having problems with the quotation marks though

also type of Board is:

type Board = [(Int,Int)]

Answer 1

Using pattern matching:

type Board = [(Int, Int)]

showTuples :: Board -> String
showTuples [] = ""
showTuples (x:[]) = show(fst(x)) ++ " " ++ show(snd(x))
showTuples (x:xs) = show(fst(x)) ++ " " ++ show(snd(x)) ++ " " ++ showTuples xs

main :: IO ()
main = putStrLn . showTuples $ [(8, 7), (5, 6), (3, 3), (9, 4), (5, 4)] -- 8 7 5 6 3 3 9 4 5 4

Answer 2

This can be done by a foldl too.

Prelude> foldl (\r (x,y) -> r ++ " " ++ show x ++ " " ++ show y) "" [(8,7),(5,6),(3,3),(9,4),(5,4)]
" 8 7 5 6 3 3 9 4 5 4"

If you don't want the preceding whitespace then just do like tail $ foldl (\\r (x,y) -> ...