Replete – a standalone ClojureScript REPL for iOS | Hacker News Reader

Replete – a standalone ClojureScript REPL for iOS

github.com

106 pointssebg21 comments

Author here. Willing to answer questions.

If I understand correctly, the ClojureScript compiler was written in Clojure (that is, you had to run the JVM to run the compiler), which spat out JS code and then compiled by Google Closure.

Would you be able to explain, at a high level, how ClojureScript bootstrapped itself, and how Google Closure comes into play?

Yes the ClojureScript compiler is written in Clojure, more than that it is written in a special form of Clojure that can do conditional branching depending on what environment it is running in. So now the ClojureScript compiler can be ran in ClojureScript.

https://github.com/swannodette/cljs-bootstrap https://github.com/clojure/clojurescript/wiki/Bootstrapping-...

Over the years the language differences between Clojure & ClojureScript have more or less been erased beyond very host specific details like String methods, no multithreading, etc. Clojure 1.7.0 landed reader conditional which permits writing conditional code based on whether the file is being compiled by Clojure or by ClojureScript.

So we simply conditionalized a few key things in the analyzer and then we just point ClojureScript JVM back at its own sources. This part was actually very simple to do. However much more challenging is the issue of macros. As with many Lisps, Clojure has only a few primitive special forms and most of the language is actually written in terms of macros. ClojureScript is no different, the macros files is longer than the analyzer or the compiler.

You can see ClojureScript's meta-circular moment here - https://github.com/clojure/clojurescript/blob/d1d3e866440626.... The macros file must load itself in order for it to be compiled into JavaScript.

Google Closure was always an additional optimization pass. The bootstrapped code we generate is still Closure compatible making it easy to run it yourself seperately as an optimization pass or to produce a single JavaScript file you can put somewhere on the Internet if you like.

Awesome work David!

One way to look at it: Replete has a bit of CLJS source which requires the reader, analyzer and compiler namespaces. When Replete's source is built (using the JVM), these additional namespaces get compiled down to JavaScript and are usable by Replete itself, in the R and E parts of the REPL. It is all JavaScript, of course, when on the device.

Google Closure is used for its dependency management (ClojureScript namespaces and how they require other namespaces). But Google Closure is not used for its optimizations (everything is built with :none mode).

Is there a way to pull libraries into the bootstrapped repl? I suspect lein (a bash script) wouldn't work.

Also: Are there talks or posts describing the future applications for bootstrapped ClojureScript?

Replete doesn't yet support using external libraries, but since the analyzer/compiler is available, I don't see any conceptual barrier preventing bootstrapped environments from consuming libraries.

David Nolen spoke a bit about Cljs-in-Cljs at the end of his Om Next talk, given at EuroClojure a few weeks ago. It's on YouTube now.

Link to said video (cljs-in-cljs) - https://youtu.be/ByNs9TG30E8?t=31m43s (link starts at cljs-specific stuff)

Discussion on HN - https://news.ycombinator.com/item?id=9848602

I have been wanting to learn Clojure for a while, but I am not an iOS guy.

I do not want to take away mfikes' thunder (super solid and amazing work by the way, sir. Saw your blog post on earlier work on /r/clojure on reddit ... I think, maybe a week or two ago), but how viable is something similar on Android?

I would LOVE to have something like on my Nexus 6 while in the park and outings with the family.

It is _extremely_ viable: The core REPL functionality is based on a few ClojureScript lines from Joel Martin's initial work for something similar for Node.

In short, to make an Android version would involve just running a JavaScript engine and hooking up a little bit of UI to send strings to it, and get strings back out of it.

Replete is open source... feel free to steal heavily from it.

Look at how simple and rough the first working version of Replete was (see demo of it at bottom of http://blog.fikesfarm.com/posts/2015-06-27-replete-a-standal...)

IMHO an Android version is just waiting to be created by someone. :)

Very cool. Very nice to see your work. Hope to learn something from you soon.

Maybe I will steal a friend's iPad to play with your stuff. Will keep track of your stuff.

Replete is in beta right now, so it simply requires signing up and making use of TestFlight. https://github.com/mfikes/replete/wiki/Beta

Also, it is a slightly older version, but if you want, you can try it directly online here: https://appetize.io/app/8hf37bv29k2zrj0v2j765xt3jr

A bootstrapped ClojureScript REPL now exists for Android. Replicator: http://tahmid.me/posts/2015-07-15-bootstrapped-cljs-repl-for...

Very nice! I'm busy learning Lisp/Scheme/Racket via CS61AS online and was thinking how nice Lisps would work on Microsoft's TouchDevelop. Have you thought about building a similar UI?

A nice aspect of this is that it is making use of a new capability of ClojureScript to bootstrap itself. This means that it can run its own compiler from within JavaScript, thus making it easy to create ClojureScript REPLs in environments where it wasn't previously possible. So long as TouchDevelop runs a JavaScript engine of some sort, it should be feasible. (Replete is evaluating ClojureScript forms directly on the device from within JS, without going to a backend via the network.)

Clojurescript.net is running an online version of the bootstrapped REPL. It works on at least some mobile devices I've checked.

Is there anything like this for javascript? A REPL for iOS that is. I searched for one a few weeks ago and there was nothing as simple as this.

https://news.ycombinator.com/item?id=9798158

Since this post is having a discussion and the previous one didn't, we've un-duped it.

Reply on news.ycombinator.com