Philipp Tessenow tessi

Erlang/Elixir syntax reference

This reference is aimed at allowing you to comfortably read erlang documentation and consume terms printed in Erlang format. It does not aim at allowing you to write Erlang code.

This is a modified version of http://elixir-lang.org/crash-course.html

Data types

Erlang and Elixir have the same data types for the most part, but there are a number of differences.

Upgrade Postgresql from 9.2 to 9.6 on an uberspace

Uberspace (an awesome german web hoster) has superb postgresql support, except that it currently only offers postgresql versions 9.2.x and 9.3.x. I run postgresql 9.6.2 on my uberspace and documented steps for a migration to postgresql 9.6 here.

My goal was to be as close to the original uberspace-postgresql-setup as possible, but I had to copy and modify some uberspace scripts so they correctly use the new postgresql version.

Warning: Here be dragons. This is what I did -- that doesn't mean you should do the same or what I did was clever. Always backup your data and maybe test on a throw-away uberspace first. If you find things to improve, let me know and I'll try to keep this updated.

What I assume you have

Mac OS X 10.10 Yosemite

Custom recipe to get OS X 10.10 Yosemite running from scratch, setup applications and developer environment. I use this gist to keep track of the important software and steps required to have a functioning system after a semi-annual fresh install. On average, I reinstall each computer from scratch every 6 months, and I do not perform upgrades between distros.

This keeps the system performing at top speeds, clean of trojans, spyware, and ensures that I maintain good organizational practices for my content and backups. I highly recommend this.

You are encouraged to fork this and modify it to your heart's content to match your own needs.

Install Software

Let's say you wanted to install this plugin: https://github.com/finnlabs/openproject-meeting. Here is how you would do it with the openproject version packaged at https://pkgr.io/apps/tessi/openproject:

cat >> /opt/openproject/Gemfile.plugins <<EOF
gem "openproject-plugins", :git => "https://github.com/opf/openproject-plugins.git", :branch => "stable"
gem "openproject-meeting", :git => "https://github.com/finnlabs/openproject-meeting.git", :branch => "stable"
EOF

Jumping, Finding, ...

Keybinding	-	Description
`Ctrl-1`	-	Move to 1st tab (work every number)
`Ctrl-p`	-	Go to anything
`Ctrl-g`	-	Go to line
`Ctrl-r`	-	Go to symbol (e.g. section and labels)
`Ctrl-m`	-	Move to bracket

	begin
	require "bundler/inline"
	rescue LoadError => e
	$stderr.puts "Bundler version 1.10 or later is required. Please update your Bundler"
	raise e
	end

	gemfile(true) do
	source "https://rubygems.org"

	class Address
	def initialize address, display_name, domain
	@address = address
	@display_name = display_name
	@domain = domain
	end

	attr_reader :address, :display_name, :domain

	def self.from_header h # returns an Array of Addresses

	WITH table_scans as (
	SELECT relid,
	tables.idx_scan + tables.seq_scan as all_scans,
	( tables.n_tup_ins + tables.n_tup_upd + tables.n_tup_del ) as writes,
	pg_relation_size(relid) as table_size
	FROM pg_stat_user_tables as tables
	),
	all_writes as (
	SELECT sum(writes) as total_writes
	FROM table_scans

	# assuming your subject is the UsersController with a method user_params

	describe UsersController do
	describe "params" do
	# per default the matcher extracts the subject and params method
	it { should permit_params(:email, :name, :role) }

	# to overwrite the params method use explicit .params_method()
	it { should permit_params(:first_name, :last_name).params_method(:other_user_params) }

	https://twitter.com/garybernhardt/status/349920138889404416

	[1] pry(main)> class Object; alias_method :&, :method; end
	=> Object

	With standard symbol to proc, &:foo evaluates to:

	{ \|x\| x.foo }

	With the "pretzel bun", &foo&:bar evaluates to: