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2 points by palsecam 5222 days ago | link | parent

> Hmm, doesn't each return the entire list that was being iterated over?


  arc> (each x '(1 2 3) (prn x))
But you're right, the iteration macros are mainly used while testing in the REPL, while it's often a code smell to see 'each or 'for in the final file, in my XP.

So yes maybe the best solution is to keep them returning nil, to not clutter the screen.

But a better one would be a better REPL that collapse the output if it gets too big. This would protect from a whole class of "mistakes". I use a web-based REPL for administrating Arc powered websites that does this (like the one at, only better). There were a thread on HN lately about a Python shell that does this too (collapsing output), unfortunately I don't remember its name.

"Improve the tools, improve the language", and not "keep the tools crappy, make the language crappier to fit the existing tools".

Current REPLs are very stupid when you think about it, and lots could be made to improve them. I mean, my Arc REPL in a terminal is not even as good as my Unix shell REPL. And I don't consider my Unix shell REPL awesome anyway.

Rah I should find you the link about the Python shell or clean the code (but it's JS anyway :-/) and show you my web REPL. Both do a bunch of trivial things that greatly improves the usability. For instance, they work on an "expression" level, not a "line" one. If you enter a multi-lines fn definition, then hit the up arrow, the whole definition is copied back in the input area, not just the last line. Mine also works with the mouse: I can click on a previous definition to copy it back in the input area, and this is much better for some cases that having to hit <UP> 20 times. Etc, etc.

Frankly, if "dynamic development with a REPL" means fighting with rlwrap, then I can be way more productive with editing a file in Emacs and a compile stage. Compiling is not that slow nowadays. Or have a look at Golang: it can even be blazing fast. Even Slime (for Emacs) is not really that better IMO.

There are even drawbacks with a REPL: you try things in it, but when you're done trying, you have to copy/paste the code to the editor window: you lose some time you would not have wasted with a static language! Big big hacks should be done in this area. Current REPLs are not good enough. That's the reason I know no Python guys that actually use `python' as a REPL. Us Lispers use one, but I guess it's mainly because we are used to it (i.e: Lisps tutorial begin by telling you to start a REPL, Python ones to start a text editor).

The ideas of making them less awkward (i.e: don't be terminal/line-oriented) and/or usable to some extend with a mouse are just little steps (but a giant leap in usability IMO). I hope some hero will come one day and will find a way to reunify the REPL and the editor window or something. Currently it's too much of a pain. How can I say, for instance, "OK, this redef I tried here in the REPL is better than the one in the source file, replace it"?

2 points by shader 5222 days ago | link

Getting better repl tools, and language integration with the repl, are two of the main things I'm interested with in arc.

I've only gotten as far as 'src and 'ppr, but I was hoping to get to the point where arc automatically documented it's current code (i.e. the stuff actually running) and made it visible through both web and repl interfaces. In theory, 'src could be used to solve the repl -> editor -> file problem. If arc kept track of the original source files, and the current 'src associated with each of those functions, then it could possibly display the diff and even update the files if you wanted it to. Heck, why not give it a git interface, so that you can add and commit changes from the repl as well.

The reason I like arc is that the language is very easy to change, and I'm hoping to change it to make it the language that is most "aware" of itself, and its current source code.

Making a better repl is certainly something I'm interested in.


2 points by akkartik 5222 days ago | link

Yeah the python shell was dreampie:


1 point by palsecam 5221 days ago | link

Yes this is it, thank you.


1 point by akkartik 5212 days ago | link

"Hmm, doesn't each return the entire list that was being iterated over?"


Ah, I wasn't going crazy after all!

  arc> (each (a b) (obj 1 2 3 4) a)
  #hash((3 . 4) (1 . 2))
So each returns the iteratee when it's a table. Looking at the source it's just outsourcing tables to maptable. I'm going to change it to return nil.


1 point by pmarin 5222 days ago | link

Try 9term. you can edit the text buffer and resend it to arc. You will need to read carefully the man page if you are not familiar with Plan 9 tools.