Unwrapping long lines in text files

michael rice

13 Aug 2010 13 Aug '10

9:38 p.m.

The program below takes a text file and unwraps all lines to 72 columns, but I'm getting an end of file message at the top of my output. How do I lose the EOF? Michael ====== unwrap.hs ====== main = do line <- getLine if null line then do putStrLn "" main else do printList (words line) 1 main printList :: [String] -> Int -> IO () printList [] _ = do putStrLn "" printList (w:[]) k = do if k+(length w) <= 72 then do putStrLn w else do putStrLn "" putStrLn w printList r@(w:ws) k = do if k+(length w) <= 72 then do putStr w putStr " " printList ws (k+(length w)+1) else do putStrLn "" printList r 1

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Bill Atkins

13 Aug 13 Aug

11:13 p.m.

Not sure if I understood what you're trying to do, but development will be easier if you minimize your IO, e.g. : maxLineLength :: Int maxLineLength = 72 wrapLine :: String -> [String] wrapLine "" = [] wrapLine line | length line <= maxLineLength = [line] | otherwise = take maxLineLength line : wrapLine (drop maxLineLength line) main :: IO () main = interact $ unlines . concatMap wrapLine . lines Now wrapLine is pure and you can use it more easily using GHCi. Removing dependencies on IO usually makes your problem easier to test and understand and your code simpler. In your example, the EOF probably happens on the call to getLine after input has run out. By using Prelude.interact, we can ignore details like that and rely on already-written functions. HTH, Bill On Friday Aug 13, 2010, at 9:38 PM, michael rice wrote:

...

The program below takes a text file and unwraps all lines to 72 columns, but I'm getting an end of file message at the top of my output.

How do I lose the EOF?

Michael

====== unwrap.hs ======

main = do line <- getLine if null line then do putStrLn "" main else do printList (words line) 1 main

printList :: [String] -> Int -> IO () printList [] _ = do putStrLn "" printList (w:[]) k = do if k+(length w) <= 72 then do putStrLn w else do putStrLn "" putStrLn w printList r@(w:ws) k = do if k+(length w) <= 72 then do putStr w putStr " " printList ws (k+(length w)+1) else do putStrLn "" printList r 1

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michael rice

14 Aug 14 Aug

12:38 a.m.

Hi Bill, Each quote of the input is on a single line. I want to unwrap lines greater than 72 characters, i.e., break them into several lines each <= 72 characters, but I don't want to break up words. and I want to retain the blank lines. So, my output is correct except for the error message. Michael ============ My input data ============ However mean your life is, meet it and live it: do not shun it and call it hard names. Cultivate poverty like a garden herb, like sage. Do not trouble yourself much to get new things, whether clothes or friends. Things do not change, we change. Sell your clothes and keep your thoughts. God will see that you do want society. Men have become the tools of their tools. I know of no more encouraging fact than the unquestioned ability of a man to elevate his life by conscious endeavor. I once had a sparrow alight upon my shoulder for a moment, while I was hoeing in a village garden, and I felt that I was more distinguished by that circumstance that I should have been by any epaulet I could have worn. -Thoreau ============ My output ============ unwrap: <stdin>: hGetLine: end of file <<<< here's my eof message However mean your life is, meet it and live it: do not shun it and call it hard names. Cultivate poverty like a garden herb, like sage. Do not trouble yourself much to get new things, whether clothes or friends. Things do not change, we change. Sell your clothes and keep your thoughts. God will see that you do want society. Men have become the tools of their tools. I know of no more encouraging fact than the unquestioned ability of a man to elevate his life by conscious endeavor. I once had a sparrow alight upon my shoulder for a moment, while I was hoeing in a village garden, and I felt that I was more distinguished by that circumstance that I should have been by any epaulet I could have worn. -Thoreau ============ Your output ========== However mean your life is, meet it and live it: do not shun it and call it hard names. Cultivate poverty like a garden herb, like sage. Do not t rouble yourself much to get new things, whether clothes or friends. Thin gs do not change, we change. Sell your clothes and keep your thoughts. G od will see that you do want society. Men have become the tools of their tools. I know of no more encouraging fact than the unquestioned ability of a ma n to elevate his life by conscious endeavor. I once had a sparrow alight upon my shoulder for a moment, while I was h oeing in a village garden, and I felt that I was more distinguished by t hat circumstance that I should have been by any epaulet I could have wor n. -Thoreau =================================== --- On Fri, 8/13/10, Bill Atkins wrote: From: Bill Atkins Subject: Re: [Haskell-cafe] Unwrapping long lines in text files To: "michael rice" Cc: haskell-cafe@haskell.org Date: Friday, August 13, 2010, 11:13 PM Not sure if I understood what you're trying to do, but development will be easier if you minimize your IO, e.g. : maxLineLength :: Int maxLineLength = 72 wrapLine :: String -> [String] wrapLine "" = [] wrapLine line | length line <= maxLineLength = [line] | otherwise = take maxLineLength line : wrapLine (drop maxLineLength line) main :: IO () main = interact $ unlines . concatMap wrapLine . lines Now wrapLine is pure and you can use it more easily using GHCi. Removing dependencies on IO usually makes your problem easier to test and understand and your code simpler. In your example, the EOF probably happens on the call to getLine after input has run out. By using Prelude.interact, we can ignore details like that and rely on already-written functions. HTH, Bill On Friday Aug 13, 2010, at 9:38 PM, michael rice wrote:

...

The program below takes a text file and unwraps all lines to 72 columns, but I'm getting an end of file message at the top of my output.

How do I lose the EOF?

Michael

====== unwrap.hs ======

main = do line <- getLine if null line then do putStrLn "" main else do printList (words line) 1 main

printList :: [String] -> Int -> IO () printList [] _ = do putStrLn "" printList (w:[]) k = do if k+(length w) <= 72 then do putStrLn w else do putStrLn "" putStrLn w printList r@(w:ws) k = do if k+(length w) <= 72 then do putStr w putStr " " printList ws (k+(length w)+1) else do putStrLn "" printList r 1

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Bill Atkins

8:59 a.m.

Right, but if you use Prelude.interact, as in my example, you don't have to worry about the EOF checking yourself - it's all handled for you. And if you use a functional style, your code will be simpler and more testable - otherwise you might as well just use an imperative language. Here's a slightly better version (uses splitAt): maxLineLength :: Int maxLineLength = 72 wrapLine :: String -> [String] wrapLine "" = [] wrapLine line | length line <= maxLineLength = [line] | otherwise = let (line, rest) = splitAt maxLineLength line in line : wrapLine rest main :: IO () main = interact $ unlines . concatMap wrapLine . lines On Saturday Aug 14, 2010, at 12:38 AM, michael rice wrote:

...

Hi Bill,

Each quote of the input is on a single line. I want to unwrap lines greater than 72 characters, i.e., break them into several lines each <= 72 characters, but I don't want to break up words. and I want to retain the blank lines. So, my output is correct except for the error message.

Michael

============ My input data ============ However mean your life is, meet it and live it: do not shun it and call it hard names. Cultivate poverty like a garden herb, like sage. Do not trouble yourself much to get new things, whether clothes or friends. Things do not change, we change. Sell your clothes and keep your thoughts. God will see that you do want society.

Men have become the tools of their tools.

I know of no more encouraging fact than the unquestioned ability of a man to elevate his life by conscious endeavor.

I once had a sparrow alight upon my shoulder for a moment, while I was hoeing in a village garden, and I felt that I was more distinguished by that circumstance that I should have been by any epaulet I could have worn.

-Thoreau ============ My output ============ unwrap: <stdin>: hGetLine: end of file <<<< here's my eof message However mean your life is, meet it and live it: do not shun it and call it hard names. Cultivate poverty like a garden herb, like sage. Do not trouble yourself much to get new things, whether clothes or friends. Things do not change, we change. Sell your clothes and keep your thoughts. God will see that you do want society.

Men have become the tools of their tools.

I know of no more encouraging fact than the unquestioned ability of a man to elevate his life by conscious endeavor.

I once had a sparrow alight upon my shoulder for a moment, while I was hoeing in a village garden, and I felt that I was more distinguished by that circumstance that I should have been by any epaulet I could have worn.

-Thoreau ============ Your output ========== However mean your life is, meet it and live it: do not shun it and call it hard names. Cultivate poverty like a garden herb, like sage. Do not t rouble yourself much to get new things, whether clothes or friends. Thin gs do not change, we change. Sell your clothes and keep your thoughts. G od will see that you do want society. Men have become the tools of their tools. I know of no more encouraging fact than the unquestioned ability of a ma n to elevate his life by conscious endeavor. I once had a sparrow alight upon my shoulder for a moment, while I was h oeing in a village garden, and I felt that I was more distinguished by t hat circumstance that I should have been by any epaulet I could have wor n. -Thoreau ===================================

--- On Fri, 8/13/10, Bill Atkins wrote:

From: Bill Atkins Subject: Re: [Haskell-cafe] Unwrapping long lines in text files To: "michael rice" Cc: haskell-cafe@haskell.org Date: Friday, August 13, 2010, 11:13 PM

Not sure if I understood what you're trying to do, but development will be easier if you minimize your IO, e.g. :

maxLineLength :: Int maxLineLength = 72

wrapLine :: String -> [String] wrapLine "" = [] wrapLine line | length line <= maxLineLength = [line] | otherwise = take maxLineLength line : wrapLine (drop maxLineLength line)

main :: IO () main = interact $ unlines . concatMap wrapLine . lines

Now wrapLine is pure and you can use it more easily using GHCi. Removing dependencies on IO usually makes your problem easier to test and understand and your code simpler.

In your example, the EOF probably happens on the call to getLine after input has run out. By using Prelude.interact, we can ignore details like that and rely on already-written functions.

HTH, Bill

On Friday Aug 13, 2010, at 9:38 PM, michael rice wrote:

...
The program below takes a text file and unwraps all lines to 72 columns, but I'm getting an end of file message at the top of my output.

How do I lose the EOF?

Michael

====== unwrap.hs ======

main = do line <- getLine if null line then do putStrLn "" main else do printList (words line) 1 main

printList :: [String] -> Int -> IO () printList [] _ = do putStrLn "" printList (w:[]) k = do if k+(length w) <= 72 then do putStrLn w else do putStrLn "" putStrLn w printList r@(w:ws) k = do if k+(length w) <= 72 then do putStr w putStr " " printList ws (k+(length w)+1) else do putStrLn "" printList r 1

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Felipe Lessa

9:17 a.m.

On Sat, Aug 14, 2010 at 9:59 AM, Bill Atkins wrote:

...

| otherwise = let (line, rest) = splitAt maxLineLength line in line : wrapLine rest

I haven't tested myself, but does this work at all? If I am reading it correctly, this is the same as let (foo, rest) = splitAt maxLineLength foo in foo : wrapLine rest In other words, no mention of wrapLine's argument 'line', and a recursive call that will bottom out and be the same as 'undefined' :). GHC would warn you, though, if you used -Wall. That expression should read: let (thisLine, rest) = splitAt maxLineLength line in thisLine : wrapLine rest Cheers, -- Felipe.

Bill Atkins

9:31 a.m.

Oof, that's what I get for making "just one little change" without testing. You're right. On Saturday Aug 14, 2010, at 9:17 AM, Felipe Lessa wrote:

...

On Sat, Aug 14, 2010 at 9:59 AM, Bill Atkins wrote:

...
| otherwise = let (line, rest) = splitAt maxLineLength line in line : wrapLine rest

I haven't tested myself, but does this work at all? If I am reading it correctly, this is the same as

let (foo, rest) = splitAt maxLineLength foo in foo : wrapLine rest

In other words, no mention of wrapLine's argument 'line', and a recursive call that will bottom out and be the same as 'undefined' :). GHC would warn you, though, if you used -Wall. That expression should read:

let (thisLine, rest) = splitAt maxLineLength line in thisLine : wrapLine rest

Cheers,

-- Felipe.

michael rice

9:41 a.m.

Hi Filipe, Bill Your corrected version works, while the original didn't, but it still produces incorrect output: However mean your life is, meet it and live it: do not shun it and call it hard names. Cultivate poverty like a garden herb, like sage. Do not t rouble yourself much to get new things, whether clothes or friends. Thin gs do not change, we change. Sell your clothes and keep your thoughts. G od will see that you do want society. Men have become the tools of their tools. I know of no more encouraging fact than the unquestioned ability of a ma n to elevate his life by conscious endeavor. I once had a sparrow alight upon my shoulder for a moment, while I was h oeing in a village garden, and I felt that I was more distinguished by t hat circumstance that I should have been by any epaulet I could have wor n. -Thoreau I don't want to break lines in the middle of words and I want to retain the original structure of the text with respect to blank lines between individual quotes. THe only thing in the input text that should change are the lines longer than 72 characters, and they should be reformatted to one or more lines less than or equal to 72 characters. Michael --- On Sat, 8/14/10, Felipe Lessa wrote: From: Felipe Lessa Subject: Re: [Haskell-cafe] Unwrapping long lines in text files To: "Bill Atkins" Cc: "michael rice" , haskell-cafe@haskell.org Date: Saturday, August 14, 2010, 9:17 AM On Sat, Aug 14, 2010 at 9:59 AM, Bill Atkins wrote:

...

| otherwise = let (line, rest) = splitAt maxLineLength line in line : wrapLine rest

Bill Atkins

12:33 p.m.

Try this one (http://gist.github.com/524460): import Data.Char maxLineLength :: Int maxLineLength = 72 trim :: String -> String trim = reverse . dropSpaces . reverse . dropSpaces where dropSpaces = dropWhile isSpace none :: (a -> Bool) -> [a] -> Bool none f = not . any f reverseBreak :: (a -> Bool) -> [a] -> ([a], [a]) reverseBreak f xs = (reverse before, reverse after) where (after, before) = break f $ reverse xs wrapLine :: String -> [String] wrapLine "" = [[]] wrapLine line | length line <= maxLineLength = [line] | none isSpace line = beforeMax : wrapLine afterMax | otherwise = beforeSpace : (wrapLine $ afterSpace ++ afterMax) where (beforeMax, afterMax) = splitAt maxLineLength line (beforeSpace, afterSpace) = reverseBreak isSpace beforeMax main :: IO () main = interact $ unlines . concatMap (map trim . wrapLine) . lines On Saturday Aug 14, 2010, at 9:41 AM, michael rice wrote:

...

Hi Filipe, Bill

Your corrected version works, while the original didn't, but it still produces incorrect output:

However mean your life is, meet it and live it: do not shun it and call it hard names. Cultivate poverty like a garden herb, like sage. Do not t rouble yourself much to get new things, whether clothes or friends. Thin gs do not change, we change. Sell your clothes and keep your thoughts. G od will see that you do want society. Men have become the tools of their tools. I know of no more encouraging fact than the unquestioned ability of a ma n to elevate his life by conscious endeavor. I once had a sparrow alight upon my shoulder for a moment, while I was h oeing in a village garden, and I felt that I was more distinguished by t hat circumstance that I should have been by any epaulet I could have wor n. -Thoreau

I don't want to break lines in the middle of words and I want to retain the original structure of the text with respect to blank lines between individual quotes. THe only thing in the input text that should change are the lines longer than 72 characters, and they should be reformatted to one or more lines less than or equal to 72 characters.

Michael

--- On Sat, 8/14/10, Felipe Lessa wrote:

From: Felipe Lessa Subject: Re: [Haskell-cafe] Unwrapping long lines in text files To: "Bill Atkins" Cc: "michael rice" , haskell-cafe@haskell.org Date: Saturday, August 14, 2010, 9:17 AM

On Sat, Aug 14, 2010 at 9:59 AM, Bill Atkins wrote:

...
| otherwise = let (line, rest) = splitAt maxLineLength line in line : wrapLine rest

I haven't tested myself, but does this work at all? If I am reading it correctly, this is the same as

let (foo, rest) = splitAt maxLineLength foo in foo : wrapLine rest

In other words, no mention of wrapLine's argument 'line', and a recursive call that will bottom out and be the same as 'undefined' :). GHC would warn you, though, if you used -Wall. That expression should read:

let (thisLine, rest) = splitAt maxLineLength line in thisLine : wrapLine rest

Cheers,

-- Felipe.

Ronald Guida

12:59 p.m.

On Sat, Aug 14, 2010 at 12:33 PM, Bill Atkins wrote:

...

Try this one (http://gist.github.com/524460)

I noticed that Bill's solution doesn't seem to work if the input text is infinite. I found a different solution, which avoids the use of reverse, and will work even if the input is infinite, as long as the words themselves are finite in length. (http://hpaste.org/fastcgi/hpaste.fcgi/view?id=29048) module Main where import Data.List combineNonEmpty :: (t -> Bool) -> t -> ([t] -> t) -> [t] -> [t] combineNonEmpty isNull zero cat [] = [] combineNonEmpty isNull zero cat xs = let (ys, zs) = break isNull xs rest = if null zs then [] else zero : combineNonEmpty isNull zero cat (tail zs) in if null ys then rest else cat ys : rest textToParagraphs :: String -> [String] textToParagraphs = combineNonEmpty null [] (concat . intersperse' " ") . lines intersperse' :: a -> [a] -> [a] intersperse' a [] = [] intersperse' a (x:xs) = x : (if null xs then [] else a : intersperse' a xs) wordWrap :: Int -> [String] -> [[String]] wordWrap maxLineLength [] = [] wordWrap maxLineLength ws = let lengths = scanl1 (\a b -> a + b + 1) $ map length ws wordCount = length $ takeWhile (<= maxLineLength) lengths wordCount' = if wordCount >= 1 then wordCount else 1 (xs, rest) = splitAt wordCount' ws in xs : wordWrap maxLineLength rest wrapParagraph :: Int -> String -> [String] wrapParagraph maxLineLength str = let ws = words str in if null ws then [""] else map unwords $ wordWrap maxLineLength ws wrapText :: Int -> String -> String wrapText maxLineLength = unlines . concat . map (wrapParagraph maxLineLength) . textToParagraphs main :: IO () main = interact (wrapText 72)

michael rice

1:20 p.m.

Hi Bill, Very clever. You are an inspiration. Michael --- On Sat, 8/14/10, Bill Atkins wrote: From: Bill Atkins Subject: Re: [Haskell-cafe] Unwrapping long lines in text files To: "michael rice" Cc: "Felipe Lessa" , haskell-cafe@haskell.org Date: Saturday, August 14, 2010, 12:33 PM Try this one (http://gist.github.com/524460): import Data.Char maxLineLength :: Int maxLineLength = 72 trim :: String -> String trim = reverse . dropSpaces . reverse . dropSpaces where dropSpaces = dropWhile isSpace none :: (a -> Bool) -> [a] -> Bool none f = not . any f reverseBreak :: (a -> Bool) -> [a] -> ([a], [a]) reverseBreak f xs = (reverse before, reverse after) where (after, before) = break f $ reverse xs wrapLine :: String -> [String] wrapLine "" = [[]] wrapLine line | length line <= maxLineLength = [line] | none isSpace line = beforeMax : wrapLine afterMax | otherwise = beforeSpace : (wrapLine $ afterSpace ++ afterMax) where (beforeMax, afterMax) = splitAt maxLineLength line (beforeSpace, afterSpace) = reverseBreak isSpace beforeMax main :: IO () main = interact $ unlines . concatMap (map trim . wrapLine) . lines On Saturday Aug 14, 2010, at 9:41 AM, michael rice wrote:

...

Hi Filipe, Bill

Your corrected version works, while the original didn't, but it still produces incorrect output:

However mean your life is, meet it and live it: do not shun it and call it hard names. Cultivate poverty like a garden herb, like sage. Do not t rouble yourself much to get new things, whether clothes or friends. Thin gs do not change, we change. Sell your clothes and keep your thoughts. G od will see that you do want society. Men have become the tools of their tools. I know of no more encouraging fact than the unquestioned ability of a ma n to elevate his life by conscious endeavor. I once had a sparrow alight upon my shoulder for a moment, while I was h oeing in a village garden, and I felt that I was more distinguished by t hat circumstance that I should have been by any epaulet I could have wor n. -Thoreau

I don't want to break lines in the middle of words and I want to retain the original structure of the text with respect to blank lines between individual quotes. THe only thing in the input text that should change are the lines longer than 72 characters, and they should be reformatted to one or more lines less than or equal to 72 characters.

Michael

--- On Sat, 8/14/10, Felipe Lessa wrote:

From: Felipe Lessa Subject: Re: [Haskell-cafe] Unwrapping long lines in text files To: "Bill Atkins" Cc: "michael rice" , haskell-cafe@haskell.org Date: Saturday, August 14, 2010, 9:17 AM

On Sat, Aug 14, 2010 at 9:59 AM, Bill Atkins wrote:

...
| otherwise = let (line, rest) = splitAt maxLineLength line in    line : wrapLine rest

I haven't tested myself, but does this work at all? If I am reading it correctly, this is the same as

   let (foo, rest) = splitAt maxLineLength foo    in foo : wrapLine rest

In other words, no mention of wrapLine's argument 'line', and a recursive call that will bottom out and be the same as 'undefined' :). GHC would warn you, though, if you used -Wall. That expression should read:

   let (thisLine, rest) = splitAt maxLineLength line    in thisLine : wrapLine rest

Cheers,

-- Felipe.

Bulat Ziganshin

12:21 a.m.

Hello michael, Saturday, August 14, 2010, 5:38:46 AM, you wrote:

...

The program below takes a text file and unwraps all lines to 72 columns, but I'm getting an end of file message at the top of my output.

...

How do I lose the EOF?

use isEOF function. even better, use interact -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com

Ben Millwood

7:07 p.m.

On Sat, Aug 14, 2010 at 2:38 AM, michael rice wrote:

...

The program below takes a text file and unwraps all lines to 72 columns, but I'm getting an end of file message at the top of my output.

How do I lose the EOF?

Michael

While many other people have shown you why you need not necessarily answer this question, I think it'd be helpful for you to hear the answer anyway. Your message is being produced because you are trying to getLine when there is no input left. This raises an exception, which, because it is not handled by your program, prints a diagnostic message and exits. Strangely, it prints this before the output of your program - this isn't terribly important, but for the sake of completeness, it's because of the different buffering characteristics of stdout and stderr, which confusingly mean that even though your program produces output and then produces an error, the error is printed immediately while the output waits until the program is terminated to be produced. I think. Something like that, anyway. So, how do you avoid the exception? You can use System.IO.isEOF [1] to check if there is input available on the standard input handle: main = do eof <- isEOF when (not eof) realMain -- when from Control.Monad, see also: unless where realMain = do realStuff Or you can let getLine throw the exception, but catch it and deal with it yourself, rather than letting it kill your program. Catching it is a little less simple, but is considerably more flexible and powerful. The exceptions situation in Haskell is somewhat complicated by the fact that the mechanism used by haskell98 has been improved upon, but the new extensible mechanism is incompatible with the old so both have to hang around. Have a look at Control.Exception [2] and System.IO.Error [3]. In either case you have 'catch' as a sort of basic operation, and more convenient things like 'try' which sort of turn an exception into a pure Either result. I'd do something like this: main = do result <- try getLine case result of Left err -> return () -- or do something diagnostic Right "" -> putStrLn "" >> main Right line -> doStuffWith line On a more general note, your main function looks a little suspect because it *always* recurses into itself - there's no termination condition. A question nearly as important as "how does my program know what to do" is "how does it know when to stop" :) [1] http://hackage.haskell.org/packages/archive/base/4.2.0.1/doc/html/System-IO.... [2] http://hackage.haskell.org/packages/archive/base/4.2.0.1/doc/html/Control-Ex... [3] http://hackage.haskell.org/packages/archive/base/4.2.0.1/doc/html/System-IO-...

Brandon S Allbery KF8NH

7:17 p.m.

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 8/14/10 19:07 , Ben Millwood wrote:

...

Strangely, it prints this before the output of your program - this isn't terribly important, but for the sake of completeness, it's because of the different buffering characteristics of stdout and stderr, which confusingly mean that even though your program produces output and then produces an error, the error is printed immediately while the output waits until the program is terminated to be produced. I think. Something like that, anyway.

My guess is he's redirecting stdout and stderr to the same file, and stderr happens to get flushed by the Haskell runtime before stdout (possibly because a flush is performed regardless when an exception is printed). It is, as you note, not really relevant to the actual logic error leading to the exception. - -- brandon s. allbery [linux,solaris,freebsd,perl] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.10 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkxnJBUACgkQIn7hlCsL25X7jACgzk4uCCP/1LBDfgtRU0vfobZI +BgAn2oabimC8tKOII6xBC+LM41oTpqd =q1sj -----END PGP SIGNATURE-----

michael rice

7:45 p.m.

Nope. No redirection. Michael --- On Sat, 8/14/10, Brandon S Allbery KF8NH wrote: From: Brandon S Allbery KF8NH Subject: Re: [Haskell-cafe] Unwrapping long lines in text files To: haskell-cafe@haskell.org Date: Saturday, August 14, 2010, 7:17 PM -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 8/14/10 19:07 , Ben Millwood wrote:

...

Strangely, it prints this before the output of your program - this isn't terribly important, but for the sake of completeness, it's because of the different buffering characteristics of stdout and stderr, which confusingly mean that even though your program produces output and then produces an error, the error is printed immediately while the output waits until the program is terminated to be produced. I think. Something like that, anyway.

michael rice

7:43 p.m.

Thanks for the caveats. I originally tried to write some pure functions to break up the long strings into ones of acceptable length, to no avail. The solution I submitted was a frustrated attempt to solve the problem *somehow* so I'd have something that worked to refer to. I can see the benefit of separating IO from pure and will approach similar problems from that standpoint in the future. Michael --- On Sat, 8/14/10, Ben Millwood wrote: From: Ben Millwood Subject: Re: [Haskell-cafe] Unwrapping long lines in text files To: "michael rice" Cc: haskell-cafe@haskell.org Date: Saturday, August 14, 2010, 7:07 PM On Sat, Aug 14, 2010 at 2:38 AM, michael rice wrote:

...

The program below takes a text file and unwraps all lines to 72 columns, but I'm getting an end of file message at the top of my output.

How do I lose the EOF?

Michael

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participants (7)

Ben Millwood
Bill Atkins
Brandon S Allbery KF8NH
Bulat Ziganshin
Felipe Lessa
michael rice
Ronald Guida