[racket-dev] Line editing in the default REPL

From: Matthew Flatt (mflatt at cs.utah.edu)
Date: Tue Nov 25 11:00:25 EST 2014

Do you have in mind making "xrepl" intended to be part of Minimal
Racket? If not, what's the mechanism for `racket` using "xrepl" when
it's available?

A similar question applies to "libeditline". Currently, for Linux and
other Unix platforms (not counting "natipkg" variants), our convention
is that native libraries are either part of the `[g]racket` executable
or they are installed separately by users through the OS's package
manager. We can't link to "libreadline" by default in a Racket
distribution, and since "libeditline" isn't typically included with
Linux distributions (as far as I can tell), it seems like we haven't
solved any problem unless we provide "libeditline". Should
"libeditline" become not only part of the Minimal Racket distribution,
but even part of the Racket executable? Or should our convention and/or
distribution infrastructure change?

At Mon, 24 Nov 2014 18:02:45 -0500, Sam Tobin-Hochstadt wrote:
> My understanding of the licensing issues is that if the code works with
> both "libeditline" and "libreadline" then it isn't a derived work of
> readline, and therefore could be licensed under the LGPL, like the rest of
> Racket. Furthermore, turning use of "libeditline" on by default wouldn't be
> linking to any GPL code, meaning that we could do that by default.
> I think we should split up the `readline` collection into `readline` and
> `readline/base` which would be what's compatible with editline, and have
> xrepl in a `readline/base` mode on by default.
> Sam
> On Mon, Nov 24, 2014 at 5:57 PM, Leif Andersen <leif at leifandersen.net>
> wrote:
> > Hello,
> >
> > When a user first starts the racket repl, it doesn't do line editing due
> > to licensing issues. For example, it would be nice if the default editor
> > would give the previous line if you hit up arrow, rather than writing
> > "^[[A".
> >
> > I have now pointed out xrepl to several users, and every time they always
> > ask me why it's not the default repl. Apparently the problem is that xrepl
> > uses GNU Readline, which is GPL. However, Asumu found that if we replace
> > requiring readline with BSD's libedit (not libeditline), everything works
> > fine due to libedit's readline compatibility. It doesn't have all of the
> > features of readline, but it does have some of the biggest ones (such as
> > being able to use arrow keys)
> >
> > What do you all think of having `(require editline)` that works for the
> > default repl, so that it gets line editing features. This would allow us to
> > also keep `(require readline)` as before, maintaining backwards
> > compatibility.
> >
> > If we do do this, this leads to the question of distribution. Would we
> > want to include libedit inside Racket distributions, or should we just link
> > to whatever the user has on their system?
> >
> > ~Leif Andersen
> >
> > _________________________
> >   Racket Developers list:
> >   http://lists.racket-lang.org/dev
> >
> >
> _________________________
>   Racket Developers list:
>   http://lists.racket-lang.org/dev

Posted on the dev mailing list.