For reference, here is the tutorial's example reformatted in a more reasonable way:
open Random
open Graphics
let rec iterate r x_init i =
if i = 1 then x_init
else
let x = iterate r x_init (i - 1) in
r *. x *. (1.0 -. x)
let main () =
self_init ();
open_graph " 640x480";
for x = 0 to 639 do
let r = 4.0 *. (float_of_int x) /. 640.0 in
for i = 0 to 39 do
let x_init = Random.float 1.0 in
let x_final = iterate r x_init 500 in
let y = int_of_float (x_final *. 480.) in
Graphics.plot x y
done
done;
ignore (read_line ())
let () = main ()
After which, if you've been in the industry for a decade or two, you will probably decide that you'd better stop wasting your time on that particular language. Besides. It just looks ugly. Almost as ugly as perl.
The Graphics module is a core Ocaml library that is always available. In order to use it, it must be linked on the command line, similar to many other languages. Installing an unrelated OpenGL binding didn't magically make "ocaml o.ml" work. Based on this and the obvious trolling of your final paragraph, I'm hesitant to believe anything you said is true.
Seriously. You are so biased that it is easier for you to believe that other people are downright lying than to accept inconvenient truth. I was running it in the interpreted mode. Isn't that how one is supposed to run tutorials code? And obviously I've added the following:
#load "graphics.cma";;
into the file first. And forgot about it, when writing the post. So no magic here. "Beautiful" syntax by the way.
And no, I wasn't trolling. I just wanted to see what that recursion would do. The code is not exactly crystal clear there, with names like start_x and such. But it really did not work. And the syntax is really ugly. And you can believe what you like.
Dont judge syntax when you are new to a language. Few syntaxes have the tendency to never grow on you, but it is surprising how most do, even when your first impressions were pretty bad. Remarkable abilities of the human brain !
Tried it here and it worked, both on Arch Linux with OCaml 4.01.0 and a clean Ubuntu/12.04 with OCaml 3.12.1:
$ ocaml graphics.cma test.ml
Debian splits OCaml into two packages: ocaml-nox (no X) and ocaml (everything). Make sure you're not using the nox version, and make sure you have an X server available (i.e. you're not running it on a headless server or something).
Still, "fatal I/O error" is a terrible error message.
http://ocaml.org/learn/tutorials/structure_of_ocaml_programs...
(someone really should go through these tutorials and fix the various misleading parts)
Basically, the rule is to use "let () = ..." for your main block / top-level code and don't use ";;" ever.