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Comment by LesZedCB | Hacker News Reader

> npm install -g lumo-cljs closh

why? seriously, is this the point that modern tooling has gotten to where for no apparent reason it has a node dependency?

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Node is the runtime for ClojureScript. The whole shell runs in Node.

what's the tradeoff of clojurescript over native clojure? wouldn't the java clojure runtime be much faster?

Steady-state performance tends to be better on the JVM but startup performance is always much better on top of JavaScript. That makes it an enticing trade off for shells which is a process that you start new ones of constantly and where the performance of the shell itself is often not very important. (Performance-critical or hard-to-duplicate code like, say, line editing code, can be done equally well on either platform via FFI.)

Why not just make a server that starts up once in the background and then a lightweight c frontend to the server that essentially just pipes every keystroke to the server?

Shells are supposed to inherit a ton of state from their parent — [e]uid, groups, working dir, env vars, nice, umask, chroot, ... This takes zero effort in unix, but would all have to be (securely!) re-implemented to be able to send code to a shared execution daemon...

And I expect the right implementation for many of these params will be running separate daemons anyway (eg. you clearly want one per user).

yes. and multithreaded.

Theres no meaningful reason to use cljs other than to avoid java or if the java runtime isn’t available (eg. browser).

startup time: not sure it's good ux to wait seconds for every command...

lumo/cljs is instantaneous

It's not like you need to spin up a separate JVM for each command.

500-600ms is, to be fair, a big one time cost.

The downsides are pretty darn significant though. I can’t imagine a situation where I would trade ‘starts a bit faster’ for ‘throw away all parallelism in code’ personally... but hey. Plenty of people use node for very serious stuff.

I suppose I just think this is an example of fast and cheap on the fast/cheap/good scale.

But this is a shell. You start _all the time_, including plenty of times where you don't really notice: other processes often start subprocesses via your shell to get your environment right. Meanwhile, the shell is usually just waiting for you, so it's not like it's an intrinsically parallel process. This doesn't impact the shell's ability to run multiple things at once: the shell eventually creates subprocesses. One would expect an event-loop like Node to be perfect for this sort of thing.

I find to hack on clojurescript on node easier. Also it is easier and starts faster.

But many parts of code are platform agnostic. I think it would be cool to eventually port the system specific parts to java apis and have both.

What does your development environment look like? Every time I bail on a Cljs project it's because tooling is worse than for Clj.

I use Spacemacs and have the following in inside my .spacemacs in the dotspacemacs/user-config functions:

      (require 'cider)                                  
      (setq cider-cljs-lein-repl                                                                             
        "(do                                        
            (require 'figwheel-sidecar.repl-api)                                                         
            (figwheel-sidecar.repl-api/start-figwheel!)
            (figwheel-sidecar.repl-api/cljs-repl))")

Then I just use figwheel to manage my cljs projects (I think this is the default now for reagent and luminus projects, it's also the default for re-natal for react native development in cljs). Life is pretty good and I have a nice debugger via Chrome.

I prefer the debugger in CIDER (which doesn't work for cljs) to the debugger in Chrome, but the Chrome debugger is decent (and it's what I'd have in Javascript anyway). There is a nice chrome extension to help with clojurescript eval in the browser/debugger called dirac: https://github.com/binaryage/dirac

Whoa, awesome. That was super helpful. I'm also a spacemacs user, but my pain was mostly for non-browser Cljs. I should have specified, you're right: developing browser Cljs is pleasant because of figwheel :)

I also use figwheel for Android development via React Native. It seems to work pretty well.

This configuration is tremendously slow for me for some reason. Looks like Chrome put a tab "to sleep" when it loses focus. That leads to long freezes while you type anything in cljs file. Am I missing anything?

Clojure/JVM apps are very slow to start, which makes them particularly unsuitable for a shell, where you typically don't want to wait a few seconds for the prompt to become interactive.

i mean, really what is the point of Node ?

It's a highly performant platform, based on a rapidly evolving language that's easy to understand. As such it's largely democratised server/shell programming to millions of users and web developers who could have been turned off by more advanced syntaxes and programming concepts. These people have created millions of open source packages which now dwarf most other communities, and the platform has unlocked an incredible amount of untapped economic value that powers likely hundreds of thousands of businesses around the world. Need I go on?

yes, and thankyou for answering. Why use Node over the JVM ?

That’s answered in the comments elsewhere on this page. Mainly because shell processes are started frequently and the JVM start-up time would be much too slow.

JVM starts pretty fast, the problem lies within Clojure's implementation.

One can even AOT to native code, if desired.

The JVM is well-known to start slowly. It's not just clojure. For example, that's why people don't write command-line scripts in scala. I mean this is what I've always read, and is my experience from my limited contact with the JVM, and this is what people who use scala tell me. If you're going to contradict a widely-held belief then you need to provide some justification! Try googling "jvm slow startup".

First of all, there are AOT native compilers for Java, making as fast to start as any other native compiled language.

Second, it is a well known fact in the Clojure community since several years, that the blame lies in Clojure itself.

http://blog.ndk.io/jvm-slow-startup.html

https://dev.clojure.org/display/design/Improving+Clojure+Sta...

> Try googling "jvm slow startup".

Its slow because a bare bones hello world takes 40ms in Java instead of 1ms in C. Its "slow" relative to other languages, but its not really that slow over all. I can use mvn without noticing that its slow, but leiningen takes multiple seconds to run a command.

Take a look at this image, taken from the link pjmlp posted: http://blog.ndk.io/img/jvm_vs_clojure.svg

Note that the Clojure team are working on improving this, but it will never be as fast as pure Java and certainly never as fast as other languages (including cljs on node)

Millions of open source packages. Right.

When you can have a package to wrap one line of code its easy to have lots of packages.

Ok, half a million. Similar order of magnitude ...

Aka BASIC.

Is this satire?

It'd better be.

I don't think it is. In the words of Bill Clinton: "it's the economy, silly". Economic/social factors trump technical aspects 99% of the time, the 1% being technical revolutions. And Java or C# or Lisp being better than Javascript doesn't fall into the "revolution" category. Ergo Javascript everywhere :)

can run Javascript on the JVM, so I'm wondering what Node has over the JVM

SV hip factor.

And yours must be one of those funny stereotypical HN jerk comments right?

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