Daniel 6temes

Contract Killer

The popular open-source contract for web designers and developers by Stuff & Nonsense

Originally published: 23/12/2008
Revised date: 15/12/2013
Original post

PwQGoo

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

ActiveModel

ActiveModel useful tool that some developers tend to overlook when getting started developing with Rails but that, well used, can add a lot of clarity and convenience to the code in some cases.

The use case of ActiveModel to have a class that behave like an ActiveRecord model, but without DB persistence. That allows, just by importing ActiveModel into a regular Ruby class, to get a lot of useful features that usually belong only to Rails models. These features include validation, serialization, callbacks, attribute methods, etc.

ActiveModel is, somehow, still a bit obscure part of Rails, but the official Rails Guide has some useful examples where we can get a glimpse of how poweful it is.

The story of ActiveModel is interesting as well. Back in 2008 there was an important schism of Rails 2 when Ezra Zygmuntowicz and Yehuda Katz developed [Merb](https://en.wikipedia.org/wiki

	import 'dart:html';
	import 'dart:async';


	void main() {

	// Create the target element.
	DivElement menuSprite = new DivElement()
	..style.height = "50px"
	..style.width = "50px"

	// Calendar
	//
	// Note: This calendar uses some ES6 features, so make sure that the code gets transpilled (f.e. with Babel) in the pipelane.
	// Also, there are no DI annotations, so it is recommended to use `gulp-ng-annotate` or equivalent.

	(function () {
	'use strict';

	angular
	.module('myModule')

	// Model

	case class Thing(id: Option[Int], name: String)

	object Thing {
	implicit val fmt = Json.format[Thing]
	}

	class Things(tag: Tag) extends Table[Thing](tag, "thing") {
	def id = column[Int]("id", O.PrimaryKey, O.AutoInc)

	dependencies:
	pre:
	- bin/create_github_statuses.sh

	test:
	post:
	- bundle exec rake factory_girl:lint
	- bundle exec rubocop --format html -o ${CIRCLE_ARTIFACTS}/rubocop_output.html
	- bundle exec brakeman -o ${CIRCLE_ARTIFACTS}/brakeman_output.json -o ${CIRCLE_ARTIFACTS}/brakeman_output.html
	- bundle exec rubycritic app lib --mode-ci --path ${CIRCLE_ARTIFACTS}/rubycritic/

	[alias]
	sync = "!git checkout master && git pull origin master && git fetch -p origin \
	&& for f in $(git branch --merged \| grep -v master \| grep -v '*'); do \
	git branch -d $f; done"
	please = push --force-with-lease
	amend = commit --amend --no-edit -a
	oops = "!git amend && git please"

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	fjs.parentNode.insertBefore(js, fjs);
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