Re: IO recursion

9 Apr 2001


      Use may write: 

main = do
          putStr "Filename plz: "
          file <- getLine
          content <- readFile file
	  let linesWithNo = map (\(lineNo, s) -> show lineNo ++ ": " ++ s) (zip
[1..] (lines content))
	  mapM putStrLn linesWithNo

then:

main
Filename plz: lines.hs
1: main = do
2:           putStr "Filename plz: "
3:           file <- getLine
4:           content <- readFile file
5: 	  let linesWithNo = map (\(lineNo, s) -> show lineNo ++ ": " ++ s)
(zip [1..] (lines content))
6: 	  mapM putStrLn linesWithNo

Cheers, 
Bernd Holzmüller

mapple apple schrieb:
...
Hi everyone,
I'm not sure this is the place to ask, coz I hvn't join your mailing
list. But anyway ..
Here's the case .. does anybody know 'bout IO recursion?
ie. We've a file and we want to put a numberline
1: 'first line'
2: 'second line'
until n, where n is the last line
I know how to convert a file into a huge string using 'readFile'
and I'm using the 'lines function' in the prelude.
That means i have a huge string like "\nHi mate\nHow r u?"
using the helper function 'lines' i can do that by saying :
main :: IO ()
main = do
             putStr "Filename plz: "
             file <- getLine
             content <- readFile file
             putStr ("1: " ++ read (show (head (lines content))))
             and so on
that's not recursive function and will not work for all cases.
So please .. if anyone knows how to do those things, let me know.
one more thing, does anybody know how to join the mailing list??
mapple apple
mapple_83@hotmail.com
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