I’m starting a new diary for my forays into learning Erlang. Below are my first entries. I basically want to learn Erlang for a couple of reasons:
- It’s a new language I don’t know
- Functional languages interest me
- I enjoy agent-based modeling and simulation
- I want to write a Wator simulation in Erlang
The reason for the final note can be traced back to a Software Craftsmanship meeting on November 10, 2008. Uncle Bob was talking about the Total Cost of a Mess and showing off his old Java crapplet code for a Wator implementation. Dean Wampler then said, and I’m paraphrasing, it would be interesting [for Gus] to implement Wator in Erlang.
11/11 @ 12:00
Some tests were running while I was at work so I installed the Erlang Mac port. The install didn’t work :( I had to modify the port to remove the - hipe line. Thanks to Brian Tatnall.
I also downloaded some documentation. Namely:
- Erlang Book - Part 1; [EB]
- Design Patterns for Simulations in Erlang/OTP; [PhD]
- Program Development Using Erlang - Programming Rules and Conventions, from Ericsson; [Zzzz]
- HTML Documentation provided with the port, same as on the site; [erl]
I haven’t written or compiled a lick of code yet, haven’t even really looked at the language. I know from past experiences that getting started is the slowest part of learning a language and that having documentation at your fingertips is the key to resolving it.
See you later. Love you. Golly … I sure am excited
11/12 @ 8:10
I didn’t get much sleep last night. Nothing to do with Erlang. I hit snooze like 3 or 4 times. I was already running late and sent an email to the team about it. Apparently my son had the same problem. I had to drive him to school, which made me late for my late train.
Thusly, I had about 50 minutes to spare before the 8:55a train, which you know is not going to get there on time because American train systems suck and never get anywhere when they’re supposed to; unless I’m running almost late and get to the train a few minutes ahead only to find that that the smart train conductors were thinking kindly and got the train there ahead of me.
All that said, time to spare. I “opened” [EB] and read through the Introduction. I really did this time. I’ll prove it: Erlang was designed for use in concurrent, real-time systems. It was designed pragmatically while some phone geeks were putting together a phone system. The language only contains what is needed and it doesn’t contain any of that gobbelty-gook sugar that sequential logic programming languages have. And it’s fast.
Next, I started chapter 1 entitled Programming. Awwweeesuuummm. First page, code; to wit:
-module(math1).
-export([factorial/1]).
factorial(0) -> 1;
factorial(N) -> N * factorial(N-1).I can type that into my editor, and did (actually, I copied it). Saved it as ch1.erl. I added the erl because I noticed there was a command of the same name and I figured I would be smart. ch1 means “chapter 1”. Oh, you betcha *wink*.
Alright. Now to run it.
Ok.
Want to run it.
Looking around for the next step; the running-it step.
Still looking.
[EB], help! Anything? What’s that you say [EB]?
[EB]: How the code for factorial was compiled and loaded into the Erlang system is a local issue.
Gus: WTF does that mean?
[EB]: By ‘local issue’ we mean that the details of how a particular operation is performed is system-dependent and is not covered in this book.
Gus: Uh huh …
[EB; page 10]
Well … that’s not very helpful. What the hell is NOT system-dependent? Diary, Erlang made me so mad! I could have just poked it in the eye; but not too hard.
I hacked around for while, farting with erl. Got a lot of this:
** exception error: bad argument in an arithmetic expression
in operator '/'/2
called as factorial / 1and this:
> import('./ch1').
exception exit: { {bad_module_name,"./ch1"},[{shell,import,1}]}and this:
> module(math1).
** exception error: undefined function shell_default:module/1and this
> import(ch1).
ok
> math1:factorial(1).
** exception error: undefined function math1:factorial/1Doh! That last one with the ok really got me. I swear to god I thought I had it. Khhhhaaaaannnnnnn!
Tried compiling with erlc. It created a file called ch1.beam. But … didn’t help. Don’t know what to do with it and I have no stinking internet access because I’m still at the train station and I don’t have one of those cool cards that lets me connect over satellite or cellular signals. Wah!
I have over 300 pages of documentation on Erlang. No lie. Where is the little bit of documentation that says, “If you’d like to actually use this turd you just wrote, do this you big dumby …”? Or maybe “If on a machine that is inferior to one of the real-time embedded systems we wrote this language for, do this …”. Seriously! Is it truly that terrible? Does it make the documentation that is linked off the site so muddied up and offend so many of others’ sensibilities? I think not.
Gobbelty-gook sugar sure would be sweet right now :( If I ever get something running and then learn this language, I will feel soooooo elite .. barf.
Done for now. Crying. I’m sad and it’s cold outside.
11/12 @ 9:58
Almost to the train station. Had a thought:
Note: When Gabriel said he didn’t like Erlang because of the syntax, what was I thinking about? Probably had something to do with unicorns, band-aids, and rock candy.
11/12 @ 19:42
Diary,
I finally got Erlang to compile something. It was our little factorial program and I did it on the way home today … on the train not in the car. It all started when I did some digging into the docs that can be found with the port and ran across “Getting Started With Erlang” [GS]. With an unlikely name like that, it’s no wonder I couldn’t figure it out.
Anyways, seems like I was almost there. I was missing one f’ing character in this whole mess. The lower-case letter ‘c’. What does it do? Well, look at this:
justin@gus ~ > erl
Erlang (BEAM) emulator version 5.6.2 [source] [async-threads:0] [kernel-poll:false]
Eshell V5.6.2 (abort with ^G)
1> c(math1).
{ok,math1}
2> math1:factorial(1).
1
3> math1:factorial(10).
3628800
4> math1:factorial(100).
93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000Yeah, it worked. I’m happy again.
Look! A unicorn with a band-aid on its corn and it’s crapping rock candy throughout the land.
Love you! Ok, ba bye.
PS: I added a great picture.
Update
- I no longer work at the place I did when I wrote this article.
