COP 4020 Lecture -*- Outline -*-

* Installing and Running Erlang

** motivation

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         MOTIVATION FOR ERLANG

Erlang designed for:

 - reliable distributed systems (telephony)

Language Design:

 - mix of functional and logic programming influences
 - actor model for concurrency and distribution

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        Q: Why this kind of design?
           - immutable data allows concurrency without locking
           - distribution allows for scalable systems, 
             avoids single point failures

        This is a very successful model of distribution and
        parallelism
           - copied in other languages (e.g., Scala)
        
** installation

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         INSTALLING ERLANG

Download erlang from:

  https://www.erlang.org/downloads

1. Double click on the download
2. Add the install directory to your PATH

On a Mac:

 - For Homebrew on OS X: brew install erlang
 - For MacPorts on OS X: port install erlang

For Linux:

 - For Ubuntu and Debian: apt-get install erlang
 - For Fedora: yum install erlang

------------------------------------------
        Q: Why this kind of design?
           - immutable data allows concurrency without locking
           - distribution allows for scalable systems, 
             avoids single point failures

** Running code

*** shell
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          RUNNING THE ERLANG SHELL

$ erl
Eshell V10.5  (abort with ^G)
1> 2+7.
9
2> halt().
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        You can also type ^C to halt the system

*** modules and files
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         CODE GOES IN MODULES

module names start with a lowercase letter

    hello

goes in a file with .erl suffix:

    hello.erl
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      See hello.erl

       % MODULE hello

-module(hello).
-export([main/0]).

main() -> 'Hello, world!'.

       notice the syntax has periods and parentheses and square
       brackets.

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        RUNNING CODE

1. Compile the module

$ erl
Eshell V10.5  (abort with ^G)
1> 


2. Run the code

2> 

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         ... c(hello).       % compile it
             {ok,hello}      % response

         ... hello:main().   % note the module name and period!
             'Hello, world!' % result