Re: Newbie question

9 Jan 2005

      Dmitri Pissarenko  writes:
...
a) asking the user to enter several numbers (while the end of the sequence is
indicated by entering 0)
b) calculate the sum of those numbers.
...
Here is a corrected version:
...
module Main where
import IO
Delete this.
...
main = do
  hSetBuffering stdin LineBuffering
This is extraneous - stdin should be line buffered by default.
...
words <- askForNumbers
  printWords words
  map read words
  putStrLn "The sum is"
  foldl (+) 0 words
Here you map read over words and discard the result.
Then you wold over the words and produce an interger,
whereas you should produce an IO value from the do block.

Here is a complete implementation (untested):

main = do 
       words <- askForNumbers
       mapM_ putStrLn words
       putStrLn "EOL"
       let nums = map read words
       print nums
       putStrLn "The sum is"
       print (foldl (+) 0 nums)

- Einar Karttunen