Day 1: Erlang Hello World

jdfolino — Mon, 30 Mar 2020 23:05:21 +0000

Ok so after being a Java and Ruby guy for 13 years it is time for me to learn some Erlang for my new job.

Hello World in Ruby is extremely easy. You just open up the terminal and run the code below:

puts 'Hello World'

My initial attempt to do something similar in Erlang found no simple one liner to do so. Below is Hello World in Erlang:

% hello.erl
-module(hello).
-export([hello_world/0]).

hello_world() -> io:fwrite("hello, world\n").

My inner nerd found a few things to get excited about:

You finish each line with a full stop. This is just so logical and makes sense. When I started with java 13 years ago I always wondered why they used a semi colon instead of a full stop.
You declare the function to export with the arity. This is cool because you can see at glance how many arguments the function will take
Function declaration on a single line could mean we have nice, concise code

How do you run this code? You open the Erlang shell, compile the code in the shell (never seen that before) and then you call the function:

1> c(hello).
{ok,hello}

2> hello:hello_world().
hello, world

c(hello). literally compiles the hello.erl file. Another neat thing is how each time you evaluate a line it updates the number in the shell.

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