matrix display error

[acapi]

It is not possible to correctly display an array in WinGHCi.

prettyMatrix $ matrix 4 4 $ \(i,j) -> 2*i - j

"\9484 \9488\n\9474 1 0 -1 -2 \9474\n\9474 3 2 1 0 \9474\n\9474 5 4 3 2 \9474\n\9474 7 6 5 4 \9474\n\9492 \9496"
it :: String
(0.00 secs, 193,072 bytes)

putStrLn it
*** Exception: : hPutChar: invalid argument (invalid character)

---

It's all OK if:

putStrLn $ filter (notElem ['\9488','\9474','\9484','\9492','\9496'] ) $ prettyMatrix $ matrix 4 4 $ \(i,j) -> 2*i - j

1 0 -1 -2
3 2 1 0
5 4 3 2
7 6 5 4

[wchresta]

This is probably an issue with your terminal/stdout not being set up to support unicode characters. This is more an issue of the environment; although I think that using unicode characters in the show instance instead of the more compatible ascii alternative should be avoided.

c.f. https://stackoverflow.com/questions/28003875/haskell-save-unicode-string-characters-to-file

[acapi]

Now I use this pretty function:

import qualified Data.Map as M

prettyMatrixASCII = putStrLn . f . prettyMatrix
    where
    f xs = map (\x -> case M.lookup x conv of
                        Nothing -> x
                        Just y  -> y) xs
        where
        conv = M.fromList [('\9488','\\'),('\9474','|'),('\9484','/'),('\9492','\\'),('\9496','/')]

With results similar to the original function:

/             \
|  1  0 -1 -2 |
|  3  2  1  0 |
|  5  4  3  2 |
|  7  6  5  4 |
\             /

However it is very inconvenient to have to repopulate this function in every module that uses Data.Matrix.

Could you insert in the library a function similar to mine?

[Daniel-Diaz]

Thanks for pinging again and providing some code. I will get this fixed over the weekend.