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haskellstdinansi-escape

Process arrow key ANSI escape sequences on haskell stdin

I'm trying to process arrow key ANSI escape sequences i.e.

up - "\033[A"
down - "\033[B"
left - "\033[D"
right - "\033[C"

in my programme so when I press the up/down/left/right arrow key, it won't have to look like this:

% stack runghc test.hs
Input a name?
^[[A^[[B^[[C^[[D^

on my stdin, but rather I would like those keys to be suppressed or even better, for them to actually work(i.e move the cursor left/right). My code is as follows:

main = do putStrLn "Input a name?"  
          name <- getLine  
          putStrLn $ ("His name is " ++ name)

Any help would be appreciated. Thanks in advance.

Solution

  • I had trouble installing the readline library due to some errors and decided to use the haskeline library, which is a more portable pure-haskell replacement for it.

    Using its syntax and modifying the earlier code, I got:

    main :: IO ()
main = do putStrLn "Input a name?"
          runInputT defaultSettings insertion
  where
      insertion :: InputT IO ()
      insertion = do
          minput <- getInputLine ""
          case minput of
              Nothing -> return ()
              Just input -> do outputStrLn $ "His name is " ++ input

    Which solves the problem as I am now able to move my cursor with the arrow keys freely without having to see any trailing ANSI escape sequences as shown below:

    result