I'm trying a little experiment in haskell, wondering if it is possible to exploit laziness to process IO. I'd like to write a function that takes a String (a list of Chars) and produces a string, lazily. I would like then to be abily to lazily feed it characters from IO, so each character would be processed as soon as it was available, a...
I have a code : main = do putStr "Test input : " content <- getLine putStrLn content And when I run it (with runhaskell) or compile it (ghc 6.10.4) result is like this: asd Test input : asd I'm new to haskell and in my opinion printing should be first. Am I right? In code sample on http://learnyouahaskell.com/ which use...
Hi, Still quite new to Haskell.. I want to read the contents of a file, do something with it possibly involving IO (using putStrLn for now) and then write new contents to the same file. I came up with: doit :: String -> IO () doit file = do contents <- withFile tagfile ReadMode $ \h -> hGetContents h putStrLn contents wit...
One last question for the evening, I'm building the main input function of my Haskell program and I have to check for the args that are brought in so I use args <- getArgs case length args of 0 -> putStrLn "No Arguments, exiting" otherwise -> { other methods here} Is there an intelligent way of setting up other methods, or is...
I've tried this: main = do hSetBuffering stdin NoBuffering c <- getChar but it waits until the enter is pressed, which is not what I want. I want to read the character immediately after user presses it. I am using ghc v6.12.1 on Windows 7. EDIT: workaround for me was moving from GHC to WinHugs, which supports this correctly...
Is there a traditional way to map over a function that uses IO? Specifically, I'd like to map over a function that returns a random value of some kind. Using a normal map will result in an output of type ([IO b]), but to unpack the values in the list from IO, I need a something of type (IO [b]). So I wrote... mapIO :: (a -> IO b) -> [a]...
Hi, I'm trying to read and decode a binary file strictly, which seems to work most of the time. But unfortunately in a few cases my Program fails with "too few bytes. Failed reading at byte position 1" I guess Binary its decode function thinks there is no data available, but I know there is and just rerunning the program works fine. ...
Hi I have a file which look like this index : label, index's value contain keys in the range of 0... 100000000 and label can be any String value, I want split this file which has 110 Mo in many slices of 100 lines each an make some computation upon each slice. How can I do this? 123 : "acgbdv" 127 : "ytehdh" 129 : "yhdhgdt" ... 989...
I'm a Haskell beginner and thought this would be good exercise. I have an assignment where I need to read file in a thread A, handle the file lines in threads B_i, and then output the results in thread C. I have implemented this far already, but one of the requirements is that we cannot trust that the entire file fits into memory. I wa...
I have a few situations where I need to list files recursively, but my implementations have been slow. I have a directory structure with 92784 files. find lists the files in less than 0.5 seconds, but my Haskell implementation is a lot slower. My first implementation took a bit over 9 seconds to complete, next version a bit over 5 secon...