Cully Larson cullylarson

Real-World Functional Programming

May 28, 2014

This code is a companion to the APIcon presentation Real-World Functional Programming by @jearldouglas and @kelleyrobinson. The slides are available here.

In this code, we compare imperative and functional implementations of a withdraw function that might be used in a banking ATM.

Imperative transactions

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.

Not all random values are created equal - for security-related code, you need a specific kind of random value.

A summary of this article, if you don't want to read the entire thing:

Don't use Math.random(). There are extremely few cases where Math.random() is the right answer. Don't use it, unless you've read this entire article, and determined that it's necessary for your case.
Don't use crypto.getRandomBytes directly. While it's a CSPRNG, it's easy to bias the result when 'transforming' it, such that the output becomes more predictable.
If you want to generate random tokens or API keys: Use uuid, specifically the uuid.v4() method. Avoid node-uuid - it's not the same package, and doesn't produce reliably secure random values.
If you want to generate random numbers in a range: Use random-number-csprng.

You should seriously consider reading the entire article, though - it's

	/*
	Node.js, express, oauth example using Twitters API

	Install Node.js:
	curl -0 http://nodejs.org/dist/v0.6.11/node-v0.6.11.tar.gz
	tar -zxf node-v0.6.11.tar.gz
	cd node-v0.6.11
	./configure
	make
	make install

	#!/bin/bash

	# Script for installing tmux on systems where you don't have root access.
	# tmux will be installed in $HOME/local/bin.
	# It's assumed that wget and a C/C++ compiler are installed.

	# exit on error
	set -e

	TMUX_VERSION=1.8

	# Hello, and welcome to makefile basics.
	#
	# You will learn why `make` is so great, and why, despite its "weird" syntax,
	# it is actually a highly expressive, efficient, and powerful way to build
	# programs.
	#
	# Once you're done here, go to
	# http://www.gnu.org/software/make/manual/make.html
	# to learn SOOOO much more.

	ssh-keygen -t rsa -b 4096 -m PEM -f jwtRS256.key
	# Don't add passphrase
	openssl rsa -in jwtRS256.key -pubout -outform PEM -out jwtRS256.key.pub
	cat jwtRS256.key
	cat jwtRS256.key.pub

	import State, {get, put, modify} from 'fantasy-states'
	import {prop, compose, map, chain, merge, always} from 'ramda'


	// Unfortunately Binary Gendered Baby Page
	//==========================================

	const babies = [{id: 2, name: 'Anjali', sex: 'F'}, {id: 3, name: 'Antonio', sex: 'M'}]

	// isFemale :: Baby -> Bool

	//http://stackoverflow.com/questions/105034/how-to-create-a-guid-uuid-in-javascript
	Math.random().toString(36).substring(2, 15) + Math.random().toString(36).substring(2, 15);

	/*
	Node.js, express, oauth example using Twitters API

	Install Dependencies:
	npm install express
	npm install oauth

	Create App File:
	Save this file to app.js