ANNOUNCE: GHC version 6.10.1 - EditLine / terminal incompatibility?

Simon Marlow marlowsd at
Fri Nov 21 09:01:11 EST 2008

Duncan Coutts wrote:
> On Thu, 2008-11-20 at 12:51 +0000, Simon Marlow wrote:
>> Duncan Coutts wrote:
>>> What I really think is that we should add back optional readline
>>> support. People building closed source ghc binaries would not use it but
>>> linux distros could enable it and provide a better "out of the box"
>>> experience. As I understand it there would be no licencing problems with
>>> that approach.
>> One downside I can see is that it gives us an extra configuration to test 
>> and maintain.  It's hard enough keeping one line-editing binding working, 
>> let alone two!
>> It's true that editline seems to have brought a bunch of headaches with it, 
>> though.  Perhaps Haskelline is the way to go in the future.
> My selfish suggestion is that we maintain the readline configuration and
> let the people who originally wanted editline support do the work to
> maintain that configuration. I get the feeling they don't care about if
> it works well, just that it's got the license they want (which is a
> perfectly reasonable position).

I propose we do this:

  * extract the GHCi UI from the GHC package, put it in the ghc-bin package
    (maybe we should rename this package to ghc-main or something).  This
    removes the editline and bytestring (for now) dependencies from the GHC

  * Move to Haskeline for the default build.  We have to bring in terminfo
    and utf8-string as bootlibs.  This gives us line-editing on Windows,
    and removes problematic external C library dependencies.

  * Make it possible to compile the ghc-bin package against readline.
    Upload ghc-bin to Hackage, so people can say
       cabal install ghc-bin -f readline
    and get a GHCi built against readline if they want.  Oops - except that
    this would mean that the ghc-main package has a variant license.  So
    maybe we have to have a separate ghc-readline package?



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