[Haskell-cafe] Can we improve Show instance for non-ascii charcters?

[Takayuki Muranushi]

Hi all,

I wrote a small package for showing values in Unicode, to be used
together with `-interactive-print`. I wish this is useful to you.

https://github.com/nushio3/unicode-show#readme

With print :

$ ghci
...
> ["哈斯克尔7.6.1"]
["\21704\26031\20811\23572\&7.6.1"]
>

With uprint :

$ ghci -interactive-print=Text.Show.Unicode.uprint Text.Show.Unicode
...
Ok, modules loaded: Text.Show.Unicode.
> ("Хорошо!",["哈斯克尔7.6.1的力量","感じる"])
("Хорошо!",["哈斯克尔7.6.1的力量","感じる"])
> "改\n行"
"改\n行"



There were several corner-cases, such as "\"" (a string with double quotation),
"\23572\&7" (\& separates the Unicode literal from the digit
character) and "3 :♡\& 5" (where :♡\& is a name of an infix value
constructor.)

If you find more corner cases, please let me know!


Best,

--------------------------------
-- Takayuki MURANUSHI
-- RIKEN Advanced Institute for Computational Science
-- http://nushio3.github.io/
-- http://www.geocities.jp/takascience/
--------------------------------


2016-02-04 20:18 GMT+09:00 Chris Wong <lambda.fairy at gmail.com>:
> Have you considered using IHaskell instead?
>
> https://github.com/gibiansky/IHaskell
>
> It supports images and interactive widgets. It shouldn't be too hard
> to make it display Unicode text.
>
> On Wed, Feb 3, 2016 at 12:37 PM, Takayuki Muranushi <muranushi at gmail.com> wrote:
>> Show instance for non-ascii characters prints their character codes.
>> This is sad for Haskell users that speaks language other than English.
>>
>>> 'A'
>> 'A'
>>> 'Ä'
>> '\196'
>>> '漢'
>> '\28450'
>>> print $ [(++"'s dad"), (++"'s mom")] <*> ["Simon", "John"]
>> ["Simon's dad","John's dad","Simon's mom","John's mom"]
>>> print $ [(++"の父"), (++"の母")] <*> ["田中", "山田"]
>> ["\30000\20013\12398\29238","\23665\30000\12398\29238","\30000\20013\12398\27597","\23665\30000\12398\27597"]
>>
>> The function that needs improvement is showLitChar in GHC.Show, which
>> currently prints any character larger than ASCII code 127 by its
>> character code:
>>
>> http://haddock.stackage.org/lts-5.1/base-4.8.2.0/src/GHC-Show.html
>>
>> showLitChar                :: Char -> ShowS
>> showLitChar c s | c > '\DEL' =  showChar '\\' (protectEsc isDec (shows
>> (ord c)) s)
>>
>> On the other hand, there is GHC.Unicode.isPrint, the predicate for
>> printable Unicode characters, that is calling on a foreign function
>> u_iswprint for the knowledge.
>>
>> https://hackage.haskell.org/package/base-4.8.2.0/docs/src/GHC.Unicode.html#isPrint
>>
>> I think one of the solution is to  import and call u_iswprint from
>> GHC.Show, too,
>> but I don't know it's against any design choices.
>>
>>
>>
>> Yesterday, I had a chance to teach Haskell (in Japanese,) and I had to
>> use English in some of the most exciting examples, like the
>> Applicative List example above. I would heartedly like to see GHC
>> improve in these directions, so that we can make more happy learning
>> materials on Haskell.
>>
>> Let me ask your opinions on what is the best way to do this (or is
>> better not to do this), before I submit something to GHC Trac.
>>
>>
>> Best,
>>
>> --------------------------------
>> -- Takayuki MURANUSHI
>> -- RIKEN Advanced Institute for Computational Science
>> -- http://nushio3.github.io/
>> -- http://www.geocities.jp/takascience/
>> --------------------------------
>> _______________________________________________
>> Haskell-Cafe mailing list
>> Haskell-Cafe at haskell.org
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>
>
>
> --
> Chris Wong (https://lambda.xyz)
>
> "I had not the vaguest idea what this meant and when I could not
> remember the words, my tutor threw the book at my head, which did not
> stimulate my intellect in any way." -- Bertrand Russell