Newbie question

[Einar Karttunen]

Dmitri Pissarenko <mailing-lists at dapissarenko.com> 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