Abe Voelker abevoelker

##Theorem:

Given fmap id = id:

fmap f . fmap g = fmap (f . g)

To prove this we're going to need a few lemmas:

The Learning Haskell guide has been moved to a git repo to enable outside contribution

A quick "how to" on what you need to do to both setup AND recover a single-server PostgreSQL database using WAL-E

WAL-E: https://github.com/wal-e/wal-e
Assuming Ubuntu 12.04 LTS ("Precise")
We'll be using S3. Make sure you have an IAM in a group with GetObject, ListBucket and PutObject on the bucket you want to use (and that it's not public).

	require 'json'
	require 'verkehr/zookeeper'

	module Verkehr
	class Brokers
	Broker = Struct.new(:id, :host, :port) do
	def to_s
	"#{host}:#{port}"
	end

	# chruby-exec 2.1.2 -- ruby y.rb
	{:a=>:foo}
	# chruby-exec 2.1.3 -- ruby y.rb
	y.rb:2: syntax error, unexpected modifier_if
	a: if true; :foo; end
	^
	y.rb:2: syntax error, unexpected keyword_end, expecting end-of-input

	# This is an example of the Stack Exchange Tier 1 HAProxy config
	# The only things that have been changed from what we are running are:
	# 1. User names have been removed
	# 2. All Passwords have been remove
	# 3. IPs have been changed to use the example/documentation ranges
	# 4. Rate limit numbers have been changed to randome numbers, don't read into them

	userlist stats-auth
	group admin users $admin_user
	user $admin_user insecure-password $some_password

	module FizzBuzz

	-- Dependently-typed FizzBuzz, about 5 years late to the party.

	-- A specification of the problem. Each constructor tells the conditions
	-- under which it can be applied, and the "auto" keyword means that proof
	-- search will be used in the context where they are applied to fill them
	-- out. For instance, applying `N` to some Nat fails unless there's a proof in
	-- scope that the argument meets the criteria.
	data FB : Nat -> Type where

	This is a preview of Tom Ellis' database query library for Haskell.

	> {-# LANGUAGE Arrows, FlexibleContexts #-}
	> -- TODO: Get rid of FlexibleContexts if we ever move the definition of s
	> -- elsewhere.
	> {-# LANGUAGE FlexibleInstances, MultiParamTypeClasses #-}
	> {-# LANGUAGE TemplateHaskell #-}
	>
	> module Karamaan.Opaleye.Examples where
	>

	RATE_LIMIT_SCRIPT = r'''
	local now = tonumber(ARGV[1])
	local required = tonumber(ARGV[2])
	local rate = tonumber(ARGV[3])
	local per_secs = tonumber(ARGV[4])
	local do_subtract = tonumber(ARGV[5]) == 1
	local full_at = tonumber(redis.call('GET', KEYS[1])) or 0
	local score, result
	if full_at < now then
	score = rate

	# Original Rails controller and action
	class EmployeesController < ApplicationController
	def create
	@employee = Employee.new(employee_params)

	if @employee.save
	redirect_to @employee, notice: "Employee #{@employee.name} created"
	else
	render :new
	end