Emacs and Julia: how to

Tooling
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Do you put it in your init.el?

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@gcv Snail is great! Thanks a lot.

I am wondering if Snail can check variable/function names and underline them if the definition is not found, like eglot. This is probably the main reason I need eglot, even though the startup time is long. Really hope this can be done with Snail.

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23

@PetrKryslUCSD Yes, I put (setq eglot-connet-timeout 180) in my init.el.

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No, I mean eglot-jl-init…

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@PetrKryslUCSD Yes, I also put (eglot-jl-init) in my init file.

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It can be done, but should really happen after Snail switches from CSTParser to tree-sitter or JuliaSyntax. I added a ticket for your feature request. It’ll definitely take me a while to find time to work on it.

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Julia Snail is very nice indeed!

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julia> methods(sin)
# 14 methods for generic function "sin" from Base:
  [1] sin(::Irrational{:π})
     @ Base.MathConstants mathconstants.jl:126
  [2] sin(::Missing)
     @ Base.Math math.jl:1580
  [3] sin(a::Float16)
     @ Base.Math math.jl:1558
  [4] sin(x::BigFloat)
     @ Base.MPFR mpfr.jl:801

See those numbers? If you have JULIA_EDITOR configured (eg. to emacs-client), and press 2 then Ctrl-q, it opens the editor on that line of that file, and grants you five extra lives. It’s the Konami-code of the Julia REPL.

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29

C-q

I had no idea this existed. I ran into 2 little problems that were easily solved.

  1. It used the environment variable VISUAL instead of EDITOR for me.
  2. I had my VISUAL set to emacsclient -f so that it would open a new Emacs frame instead of reusing an existing one, and the way julia invoked it didn’t work. I had to change VISUAL back to just emacsclient, and then it worked.

PS: Where is this C-q feature documented?

UPDATE: 2024-12-12: I missed that you used the JULIA_EDITOR environment variable. I’d like to keep the value of VISUAL to emacsclient -f, so it’s nice that I can use JULIA_EDITOR in a Julia-specific way.

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C-q documentation here:

^Q
Write a number in REPL and press ^Q to open editor at corresponding stackframe or method

It works great for opening source files at a numbered location in a stack trace, when you encounter errors.

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Skimming through the list of keybindings, you can tell the Julia REPL was designed by an Emacs user. It’s funny seeing words like kill and yank used outside of Emacs.

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32

Update concerning a Julia REPL in Emacs 29.1.4 running in WSL 2:

  1. Julia Snail is very nice indeed. I did not get to use the remote capability, so I can’t comment. I’m not sure how I feel about the ability to evaluate code within a module. Maybe I’m just not used to it.
    Unfortunately, clicking on errors in the *julia* error buffer only works at the top.
    Error links such as the one on line 6 open a dialogue asking for a path.

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  2. julia-repl is great! I like that everything is in the command window, and the links to errors are clickable.

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    Both of the above were used with julia-mode. I haven’t tried out treesitter yet.
    Edit: Also, both used with vterm. The only thing that needed a bit of tweaking was copying from the vterm window. But it works great overall.
    Edit 2: Links in the error messages from Julia Snail are not clickable.

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33

Thank you, @gcv, for saving us from this. I’m thankful that I can move between multiple Julia projects with ease using a single Emacs instance.

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My first thought was that practically everyone uses Revise now. However, I just discovered a case where this module-aware feature is still useful.

Apparently, Revise doesn’t notice when I modify a macro in a module. I modified a few other random things in the module to verify Revise was otherwise working, and it was. However, changes to a macro were never picked up. I needed to julia-snail-send-dwim while my cursor was in the macro code to get the REPL to get the latest macro code.

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That’d be this issue, maybe? Changes to macros are ignored · Issue #20 · timholy/Revise.jl

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I run my Julia REPLs in shell buffers. If you give Meta-x shell a numeric argument it will prompt you for a new buffer name. I typically have a shell buffer for each project I’m currently wrking on.

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37

That’s a clever way to do it. Do you also have a way to send Julia code to these various shell buffers? (I did a little investigation before posting, and I found the comint-send-string function which could be used for this, but it seems like you’d have to write your own interactive function that wraps it …unless I missed something which is very possible.)

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Nothing clever, just Meta-w from one buffer and Ctrl-y in the other.

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39

Maybe you could give isend a try; it’s purpose is exactly this: send code from a buffer to a terminal. In a way that’s configurable enough to work the same for multiple types of interpreters (shell, [i]python, julia…) and multiple types of terminals (ansi-term, vterm…). It does not have specific code for shell but I just tested and it seems to work.

Disclaimer: I’m the author of this library

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Long time julia-repl user here, I just wanted to add that it is totally possible to use multiple repls in julia-repl!

The idea is that you can define a repl suffix, and the code gets send to the repl buffer with the corresponding suffix. Thus it is possible to have *julia-project1* and *julia-project2* repls. And since emacs is emacs you can obviously automate this by defining function advice, using project load hooks and so on.

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