getting_started.xml

<?xml version="1.0" encoding="iso-8859-1" ?>
<!DOCTYPE chapter SYSTEM "chapter.dtd">
<chapter>
  <header>
    <title>Getting Started</title>
    <prepared>Matthias Lang</prepared>
<docno></docno>
<date>2007-09-12</date>
    <rev>1.0</rev>
    <file>getting_started.xml</file>
  </header>

<section><title>How long does it take to learn Erlang?</title>
<p>

	It depends. (did you expect anything else?)
	</p><p>
	With an imperative language background (e.g. C, Python, Java, C++, 
	Pascal, PERL, etc.),
	it takes most people about a week before they can write 
	nontrivial programs, about a month to feel really comfortable
	and a few months before feeling ready to take on something
	big by themselves. It helps a lot to have someone who knows
	how to use Erlang around for some hand-holding.
	</p><p>
	With a background which includes another declarative language
	(Lisp, Prolog, Haskell, Scheme, etc.), you'll be able
	to hack Erlang code straight away, though learning to take
	advantage of the fault tolerance and concurrency takes a while.
</p>
</section>
	
<section><title>How can I learn Erlang?</title>
<p>

	There's an <url href="http://www.erlang.org/course/course.html">
	online tutorial</url>. Any of the
	<seealso marker="obtaining#books"> Erlang books</seealso> can 
        also be used as tutorials.
	</p><p>

	The Erlang distribution includes a step-by-step <em>getting
	started</em> guide. This is also 
	<url href="http://www.erlang.org/starting.html">online</url>
	</p><p>

	<url href="http://www.erlang.se/training/index.shtml">
	Ericsson</url> run training courses for Ericsson employees.
	</p><p>

	<url href="http://www.erlang-solutions.com/">erlang-solutions.com
	</url> and <url
	href="http://www.erlang-services.com/">erlang-services.com</url>
	both run training courses (primarily in London and Stockholm,
	but also in the US, Asia and Australia) aimed at
        businesses.
	</p><p>

	Many <seealso marker="introduction#universities">universities
        </seealso> run 
	courses either partly or wholly about Erlang. Courses about
	functional programming are also useful for getting a solid
        grounding which will then let you easily learn Erlang by yourself.
</p>
</section>

<section><title>What does "hello world" look like?</title>
<p>
	Here's one way to write hello world:
</p>

	<code><![CDATA[
	-module(hello).
	-export([hello_world/0]).
	
	hello_world() -> io:fwrite("hello, world\\n").
	]]></code>

<p>
	To compile this, save it in a file called <c>hello.erl</c> and
	compile it from the erlang shell. Don't forget the full-stop 
	("period" in American English) at the end of each command, as shown: 
</p>

	<pre>
	Erlang (BEAM) emulator version 4.9.1 [source]

	Eshell V4.9.1  (abort with ^G)
	1> c(hello).
	{ok,hello}
	</pre>
<p>

	(on unix systems you start the erlang shell by typing "erl" at the 
	command line. On Windows, open a command prompt window and
	type "werl", or find the Erlang icon in the programs menu). 
	To run the program from the Erlang shell:
</p>

	<pre>
	2> hello:hello_world().
	hello, world
	ok
	</pre>
</section>

<section><title>How do I quit the Erlang shell?</title>
<p>
	To shut a system down cleanly, use <c>init:stop().</c>
	</p><p>

	Some quick ways are evaluating <c>halt().</c> or 
	<c>Control+\</c>.
	</p><p>

	<c>Control+C</c> and <c>Control+G</c>
	give you access to menus.
	</p>
</section>

<section><title>Why does Erlang print "ok" after my program's output?</title>
<p>
	The Erlang shell works by <em>r</em>eading an 
	Erlang expression,
	<em>e</em>valuating it, 
	<em>p</em>rinting the result and 
	<em>l</em>ooping
	for another expression, i.e. a REPL shell.
	</p><p>

	The <c>io:fwrite()</c> function does two things. 
	It prints out "hello world" and it returns the value 
	<c>ok</c>.
	</p><p>

	So, when you execute <c>io:fwrite("hello, world\n")
	</c> in the shell, the <c>fwrite</c> 
	function prints the first line and the shell prints the return 
	value, <c>ok</c>. This can be 
	avoided by <seealso marker="how_do_i#noshell"> running 
        Erlang without a shell</seealso>.
</p>
</section>
</chapter>