David Corking dcorking

The thing that students have the hardest time on when learning functional programming is how to process a recursive structure while maintaining some sort of "state", the result if you will. I'll attempt here to demystify the process.

Functional programming languages almost always use a lot of recursively defined structures. Depending on the language those can be implemented in various ways, but in any case the end result is the same. A structure of this type is either an "atom", i.e. an irreducible thing, or a "compound" consisting of substructures of the same form.

For example a "list" is either an Empty/Nil list (the "atom") or it is formed as a Cons of a value and another list (compound form). That other "sublist" can itself be empty or another cons and so on and so forth. A tree is similar. It is either empty, or it consists of a triple of a value and two sub-trees, left and right.

Almost every problem we encounter is a question about doing something with all entries in a structure. To solve these prob

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Install Folding@home FAHClient on Linux as a systemd service unit

Republished on my website, keeping this version here for historical reasons.

Install FAHClient as documented in the official guide. Stop the traditional init script service that was created and automatically started.

	# Available cops (167) + config for /Users/tomaskorcak/dev/gooddata-ruby:
	# Type 'Lint' (32):
	AmbiguousOperator:
	Description: Checks for ambiguous operators in the first argument of a method invocation
	without parentheses.
	Enabled: true

	AmbiguousRegexpLiteral:
	Description: Checks for ambiguous regexp literals in the first argument of a method
	invocation without parenthesis.

	import math.abs

	object finding_fixed_points {
	val tolerance = 0.0001 //> tolerance : Double = 1.0E-4
	def isCloseEnough(x: Double, y: Double) =
	abs((x - y) / x) / x < tolerance //> isCloseEnough: (x: Double, y: Double)Boolean
	def fixedPoint(f: Double => Double)(firstGuess: Double) = {
	def iterate(guess: Double): Double = {
	val next = f(guess)
	if (isCloseEnough(guess, next)) next

	# put this in your staging.rb file. Obviously you'll need more config than this it's just an example.

	Rails.application.configure do
	config.action_mailer.preview_path \|\|= defined?(Rails.root) ? "#{Rails.root}/test/mailers/previews" : nil
	config.autoload_paths += [config.action_mailer.preview_path]

	routes.append do
	get '/rails/mailers' => "rails/mailers#index"
	get '/rails/mailers/*path' => "rails/mailers#preview"
	end

	# This is not the official way to prune directories, but I found it easier.
	# It prints the contents of all the files in the tree - excluding .git and CachedPixmaps,
	# but there is a potential bug in the second globbed file name
	#
	# Works with GNU findutils. Might not work with BSD find, such as Mac OS X.

	find -not -wholename './.git' -not -wholename 'CachedPixmaps*' -type f \|xargs cat

	# DOCKER-VERSION 1.2.0
	FROM centos:centos6

	# Enable EPEL for Node.js
	RUN rpm -Uvh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm
	# Install Node.js and npm
	RUN yum install -y npm

	# Creates a new folder on the container
	VOLUME /src

	# this looks interesting
	du --max-depth=1 -b -k /var/cache/apt \| sort -k1 -rn

	#!/bin/bash
	# exports DNS records from Rackspace Cloud DNS to text files
	# Depends on https://github.com/wichert/clouddns/blob/master/src/clouddns.py

	set -e

	me=export-zone
	base_domain=
	rackspace_region=
	rackspace_rate_limit_delay=3