Gabriel Ciuloaica devsprint

Applied Functional Programming with Scala - Notes

1. Mastering Functions

A function is a mapping from one set, called a domain, to another set, called the codomain. A function associates every element in the domain with exactly one element in the codomain. In Scala, both domain and codomain are types.

val square : Int => Int = x => x * x

Category theory jargon cheat sheet

A primer/refresher on the category theory concepts that most commonly crop up in conversations about Scala or FP. (Because it's embarassing when I forget this stuff!)

I'll be assuming Scalaz imports in code samples, and some of the code may be pseudo-Scala.

Functor

A functor is something that supports map.

The introduction to Reactive Programming you've been missing

(by @andrestaltz)

This tutorial as a series of videos

If you prefer to watch video tutorials with live-coding, then check out this series I recorded with the same contents as in this article: Egghead.io - Introduction to Reactive Programming.

Introduction to Kafka

Kafka acts as a kind of write-ahead log (WAL) that records messages to a persistent store (disk) and allows subscribers to read and apply these changes to their own stores in a system appropriate time-frame.

Terminology:

Producers send messages to brokers
Consumers read messages from brokers
Messages are sent to a topic

slow

This bash script offers quick shortcuts to simulate slower network connections. It is useful when you need to simulate a wireless network on a Linux network server, especially when you are using a virtual machine guest on your local machine or in the cloud.

slow 3G                   # Slow network on default eth0 down to 3G wireless speeds
slow reset                # Reset connection for default eth0 to normal
slow vsat --latency=500ms # Simulate satellite internet  with a high latency
slow dsl -b 1mbps         # Simulate DSL with a slower speed than the default

slow modem-56k -d eth0 # Simulate a 56k modem on the eth1 device. eth0 is unchanged.

	<?xml version="1.0" encoding="UTF-8"?>
	<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.example</groupId>
	<artifactId>cassandra</artifactId>
	<version>1.0-SNAPSHOT</version>

	<properties>
	<maven.compiler.source>1.6</maven.compiler.source>

	# Allways a good idea to sync with the formular repository first
	alex$ brew update

	# List available version
	alex$ brew versions zmq
	3.2.2 git checkout ab8de4b /usr/local/Library/Formula/zeromq.rb
	2.2.0 git checkout 6a2e6ef /usr/local/Library/Formula/zeromq.rb
	2.1.11 git checkout 497b13a /usr/local/Library/Formula/zeromq.rb
	2.1.10 git checkout 4c8ed3a /usr/local/Library/Formula/zeromq.rb
	2.1.9 git checkout 381c97f /usr/local/Library/Formula/zeromq.rb

	object Put extends Controller {
	def index = DecodeProtobuf(classOf[MyProtobuf]) { stack :MyProtobuf =>
	Action {
	// do something with stack
	}
	}
	}

	upstream your-app {
	# fail_timeout=0 means we always retry an upstream even if it failed
	# to return a good HTTP response (in case the Unicorn master nukes a
	# single worker for timing out).
	server unix:/tmp/your_app.socket fail_timeout=0;
	}

	server {
	listen 80;