Integrating editline with ghc

[Simon Marlow]

Christian Maeder wrote:

> Depending on what the ghc team and the library maintainers decide,
> either "readline" has to be changed to "readline-compat" in *.cabal or
> (worse) we get packages Shellac-readline and Shellac-editline or (more
> worse) Shellac-readline stays as is and I have to fiddle with editline
> or readline on Macs myself (like now).

It would be a bad idea to remove functionality from the readline package. 
It's a binding to the GNU readline library, and as such it does a fine job.

In a similar vein, we should have an editline package that provides a 
binding to libedit.

For convenience, we would like there to be an API that can be supported by 
both readline and editline.  It would be a bad idea for this to be a 
package, because (as I mentioned earlier on libraries@) that package would 
have a variant license, depending on whether the API-provider was readline 
or editline at build-time (or perhaps in the future link-time or run-time). 
  If you chose between readline and editline, then you have to make an 
explicit choice in your .cabal file - making a package that abstracts this 
choice is not good, unless said package is explicitly GPL'd.

So the compatible API could be in a module that is exposed by *both* 
readline and editline, say System.Console.ReadlineCompat.  So your source 
code wouldn't have to change to switch from one to the other, just your 
.cabal file.

Cheers,
	Simon