Try Erlang, a hands-on tutorial | Hacker News Reader

Try Erlang, a hands-on tutorial

tryerlang.org

66 pointssdp24 comments

Some notes after doing a few steps of tutorial:

- a simple command history feature in the shell would be really nice

- I wish the notification that I don't follow tutorial didn't appear there each time I try to play with the shell - well, I like the tutorial but I want to play on my own for a few moments, and this message is quite a distraction

- also, proceeding to next step of the tutorial could be done in some other way - e.g. I see logical operators and I try some of them, and they all disappear when i type one; it would be much easier for a newbie to learn some erlang if they stayed a bit longer on the screen

- there should be a 'back' button in some visible place too - e.g. next to clear window and reset - I can't find it at the moment

EDIT#1: formatting

EDIT#2: well, it seems that history is there - it just didn't work for some reason in my browser when I started. At the moment I am stuck in lists and tuples - whatever I do in 'Building a list' section I got a message it is not I am meant to do - is the tutorial bugged (or is it my browser again)?

Building a list doesn't work for me either. It gives every indication that I succeeded in creating a list, but the tutorial tells me I'm not doing the right thing. =(

Don't get me wrong, I respect these try-X efforts. But they have glaring annoyances (usually popping up in the name of Security) that are just begging me to open a good old-fashioned command-line REPL (but that's if I'm at my own computer).

For instance, in Try Erlang, io:format is out of reach, not to mention spawn. Same goes for Try Clojure: there doesn't appear to be a way to create threads.

Don't you think, given the languages we're talking about here, that these projects are self-handicapping from the start? (the seriousness of those security measures notwithstanding)

I'm getting the feeling that these online REPLs were created just to show that it's possible to do, not to address any practical concern or to highlight a strength of these languages.

Again, I don't mean to disparage the efforts of the authors. Just my $0.02

I think these sites are trying to cater more toward FUD-encumbered newbies than those for whom installing and having a play with a new language is second nature.

Would the down-voter care to explain their rationale?

I made Try Haskell and purity and types are Haskell's whole thing, so technically I can teach the good stuff about Haskell without needing IO and threads and such. The security measure for disabling IO was to merely not run in the IO monad. Interestingly, there is a completely pure filesystem library for Haskell http://lambda-the-ultimate.org/node/1036 that I'm thinking of using, to demonstrate the difference between side-effectual and pure functions. I agree regarding the other two, security is a big problem for them. I'm trying to get a trylisp setup but many of the Lisp guys think it's fairly impossible to do a safe sandbox.

Very nice so far. The online REPL tutorials are always a great opportunity to try something new quickly.

"Operations on integers (and floats) include addiction.." Just a rather amusing typo in one of the first sections.

Yea, I'm with you - this is a great way to get people tinkering with a new language. Does anyone know of any similar websites for for playing with other languages? I'd love to see a language test drive site with as many languages as possible in a format like this.

http://tryruby.org

http://tryhaskell.org

http://try-clojure.org

It’s pretty annoying to have to type “.” after every expression. I’m sure there’s a reason for it in Erlang, but perhaps it would be better for the tutorial to automatically add it for you for the first few sections of the tutorial, until you learn what it really means, and come upon a situation where you finally don’t want it. At the very least, a clearer warning message than “syntax error” should be shown if you forget the dot, in one of those fading black rectangles.

i think it's good that it makes you type it as it quickly becomes a habit and you need the practice when you first start erlang.

However, perhaps he can put a big floating arrow pointing left that just sits there saying "DONT FORGET THE PERIOD" as soon as you hit enter without a period.

I got a 503, anyone else does?

It was up 15 minutes ago. My guess is there were too many concurrent users.

Ironic for erlang..

I kid.. I kid

Glad you got the joke. :)

Either that or they just had to take the site down temporarily to install some new code.

Just in case anybody else got confused:

You don't take down an Erlang system to upgrade the code, you simply cause the nodes to update themselves, by sending them a message.

It's back up now!

still down ?

several hack attacks, he says he's discussing them tomorrow: twitter.com/prof3ta

This video is also a great way to get up to speed on Erlang: http://www.youtube.com/watch?v=qyVvGjNjBOA

This is not exactly what was requested by the current tutorial step. Feel free to play with the shell, anyway.

Erlang R13B04 (erts-5.7.5) > node(). "This functionality has been disabled for security reasons in tryerlang.org." > q(). "This functionality has been disabled for security reasons in tryerlang.org." > ls(). "This functionality has been disabled for security reasons in tryerlang.org." >

first thing i did, lists:map(fun(X) -> X * 2 end, lists:seq(1,100)), and it worked! very cool.

next thing i did: application:which_applications(), and that didn't work.

Expressions using arithmetical operators

Operations on integers (and floats) include addiction[sic]

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