[exercise] 10.4

Author: Dev-XYS

chapter10-Interactive-programming/4.hs

@@ -0,0 +1,16 @@
+getInt :: IO Int
+getInt = do s <- getLine
+ return (read s :: Int)
+
+addN :: Int -> IO Int
+addN 0 = do return 0
+addN n = do m <- getInt
+ s <- addN (n - 1)
+ return (m + s)
+
+adder :: IO ()
+adder = do putStr "How many numbers? "
+ n <- getInt
+ s <- addN n
+ putStr "The total is "
+ putStrLn (show s)