[racket-dev] Line editing in the default REPL

On Wed, Dec 3, 2014 at 6:22 PM, Sam Tobin-Hochstadt
<samth at cs.indiana.edu> wrote:
> On Wed, Dec 3, 2014 at 6:10 PM, Eli Barzilay <eli at barzilay.org> wrote:
>>
>>>> If you're talking about implementing line editing yourself, then my
>>>> personal reaction to that would be "wonderful", but doing it properly
>>>> is something that is difficult and easy to underestimate....
>>>
>>> I've already done this (admittedly it only works on OS X, but most
>>> Linux terminals work exactly the same with a few different
>>> constants). You can see what I have so far here:
>>> https://github.com/LeifAndersen/racket-line-editor/blob/master/main.rkt
>>
>> If this works, I'd be thoroughly impressed -- so I tried it.  I ran
>> through a bunch of configurations that I use:
>
> None of which was OS X, which was what Leif's email explicitly said it
> _only works on_.

My point wasn't "it doesn't work outside of OSX", I was talking about "a
few different constants" being a bad underestimation: they're not few,
they're not constant, and the interfaces for getting them is what you'd
expect from something that started to grow in the 70s.


> I think we should wait till he has a version which he says works
> before telling people to avoid making contributions.

You should re-read my email: if there's anything that I'm telling, it's
the exact opposite.  A point that I repeated more than once.

The thing is that it would be easy to not say anything, and watch this
approach of "try a few escapes and see what works" fail.  And it will
fail, because, again, they're not constant, and you can't just get some
magic combination that works for 90% of the people -- even just xterm on
just linux is something that can (and often is) configured in many
different ways.  So what I'm doing is the opposite: I point at how such
a thing should be written for it to survive -- but I appreciate Leif's
time enough to warn him that this is a much bigger thing than what he
seems to think.

(And to be clear, the reason for this is that I've seen probably around
3 to 5 serious attempts that got dumped; and I have encountered these
issues multiple times, so I know that it's hard enough that even getting
simple code to work, code that I intended only for my own use, even that
was pretty hard, enough to go chase old VT references and obscure man
pages.)

-- 
          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                    http://barzilay.org/                   Maze is Life!