Re: parinfer-mode for Emacs might be neat for encouraging Lisp adoption

[Oleh Krehel]

Marcin Borkowski <address@hidden> writes:

> On 2015-11-12, at 00:30, Christopher Allan Webber <address@hidden> wrote:
>
>> Here's a project borrowing some neat ideas from Emacs and extensions
>> (especially paredit) on lisp editing and providing some of its own
>> ideas, too:
>>
>>   http://shaunlebron.github.io/parinfer/index.html
>>
>> I could imagine this could make GNU Emacs an even better lisp hacking
>> environment for some than it already is, or make jumping in easier, for
>> some people.  Maybe someone will be inspired and add a plugin for it?
>> There's a space listed for editor implementations here:
>>
>>   http://shaunlebron.github.io/parinfer/index.html#editor-plugins
>>
>> I don't have time to work on this, but I imagine someone on this list
>> might find it interesting enough to take for a spin, so I thought I'd
>> post it here.  At the very least, it's clearly critical for GNU Emacs to
>> be the most advanced lisp editing environment there is. ;)
>
> Oleh's lispy does a similar (though not identical) thing.

I've looked through the Parinfer web page and I don't think it's a great
idea (it's a neat trick though):

- It doesn't solve the problem of pasting unbalanced code.
- It relies on indentation to guess the thing to do.
- The thing to do might be surprising.
+ It balances parens for potentially generic commands that know nothing
  of Parinfer.

I think the first 3 negative points probably outweigh the single
positive point. Still, it would be cool to try it if anyone is up for
implementing it.

By the way, is anyone else on emacs-devel using lispy?  It's a really
cool way to quickly navigate, edit, examine, and debug Elisp.  It was
intended to be an easier Paredit, so picking it up shouldn't be too
hard, but it will probably take a long while to pick up everything and
reach top efficiency. See https://github.com/abo-abo/lispy if you're
interested.

It also has a bunch of integration tests (I saw this discussed in a
recent thread). The tests look like this:

    (should (string= (lispy-with "(|(a) (b) (c))" "j")
                     "((a) |(b) (c))"))

The parts are:

1. The buffer state before, including point and mark.
2. The user input.
3. The buffer state after, including point and mark.

There are around 700 of these tests and they run very fast, around 1.5s
to finish all of them. I think it would be cool for ERT to have this
kind of interface, and functions like `forward-list', `up-list',
`beginning-of-defun' etc could be tested this way.

These type of tests are also a good way to learn new bindings (since
they're built into the test), and what they should do in specific
situations (since it's not easy for the user to experience each
situation which results in a different branch taken by the command in
question).