How to hack GHCi (or Hugs) so that it prints Unicode chars unescaped?

Question

Look at the problem: Normally, in the interactive Haskell environment, non-Latin Unicode characters (that make a part of the results) are printed escaped, even if the locale

Answer 1

One way to hack this is to wrap GHCi into a shell wrapper that reads its stdout and unescapes Unicode characters. This is not the Haskell way of course, but it does the job :)

For example, this is a wrapper ghci-esc that uses sh and python3 (3 is important here):

#!/bin/sh

ghci "$@" | python3 -c '
import sys
import re

def tr(match):
    s = match.group(1)
    try:
        return chr(int(s))
    except ValueError:
        return s

for line in sys.stdin:
    sys.stdout.write(re.sub(r"\\([0-9]{4})", tr, line))
'

Usage of ghci-esc:

$ ./ghci-esc
GHCi, version 7.0.2: http://www.haskell.org/ghc/  :? for help
> "hello"
"hello"
> "привет"
"привет"
> 'Я'
'Я'
> show 'Я'
"'\Я'"
> :q
Leaving GHCi.

Note that not all unescaping above is done correctly, but this is a fast way to show Unicode output to your audience.