jcoglan

The Myers diff algorithm

The following based on Myers' original paper.

The edit graph

To use the example from the paper, say you want to calculate the difference between two strings:

rlburkes

# Wouldn't it be great if you could have STI like functionality
# without needing to encode strings of class names in the database?
# Well today is your lucky day! Discriminable Model is here to help.
#
# Simply specify your models desired type column, and provide a block to
# do the discrimination. If you want the whole STI-esque shebang of properly
# typed finder methods you can supply an array of 'discriminate_types' that will
# be used to apply an appropriate type.
#
# class MyModel < ActiveRecord::Base

SamSaffron

# speed up pluck

class ActiveRecord::Relation

  class RailsDateTimeDecoder < PG::SimpleDecoder
    def decode(string, tuple=nil, field=nil)
      if Rails.version >= "4.2.0"
        @caster ||= ActiveRecord::Type::DateTime.new
        @caster.type_cast_from_database(string)
      else

jcoglan

An ActiveRecord conundrum

I'm going to describe a weird problem I faced when using ActiveRecord today. To protect the innocent, I'm not going to talk about the app I'm actually working on but will instead discuss a hypothetical but isomorphic database design for a clone of the popular blogging platform Tumblr.

Tumblr lets you publish various different sorts of content. We might be tempted to shove all these types in a big STI table, but the types are all quite different from one another and so we give them their own tables.

rietta

#
# PostgreSQL writes two optional commands to the database schema
# file, called db/structure.sql, that can only be run as a root
# database user.  These are not needed actually, so comment them
# out automatically
#
# CREATE EXTENSION IF NOT EXISTS plpgsql WITH SCHEMA pg_catalog;
# COMMENT ON EXTENSION plpgsql IS 'PL/pgSQL procedural language';
#
namespace :db do

ernie

#!/usr/bin/env ruby

class Module
  private

  def delegate(*args)
    dest, prefix = _extract_valid_delegation_options(args.pop)
    _define_delegators(caller_locations.first, prefix, dest, args)
  end

rgs

Falsehoods programmers believe about prices

1. You can store a price in a floating point variable.
2. All currencies are subdivided in 1/100th units (like US dollar/cents, euro/eurocents etc.).
3. All currencies are subdivided in decimal units (like dinar/fils)
4. All currencies currently in circulation are subdivided in decimal units. (to exclude shillings, pennies) (counter-example: MGA)
5. All currencies are subdivided. (counter-examples: KRW, COP, JPY... Or subdivisions can be deprecated.)
6. Prices can't have more precision than the smaller sub-unit of the currency. (e.g. gas prices)
7. For any currency you can have a price of 1. (ZWL)
8. Every country has its own currency. (EUR is the best example, but also Franc CFA, etc.)

bf4

# use inverse_of to 'just work'
class User < ActiveRecord::Base
  has_many :contributions, inverse_of: :user
  has_many :posts, through: :contributions
end

class Post < ActiveRecord::Base
  has_many :contributions, inverse_of: :post
  has_many :contributors, through: :contributions,
    source: :user

carlzulauf

#!/usr/bin/env ruby
 
# thin init script
# install to /etc/init.d/thin

# crazy debian LSB header stuff
### BEGIN INIT INFO
# Provides:          thin
# Required-Start:    $local_fs $remote_fs
# Required-Stop:     $local_fs $remote_fs

dergachev

OS X Screencast to animated GIF

This gist shows how to create a GIF screencast using only free OS X tools: QuickTime, ffmpeg, and gifsicle.

Instructions

To capture the video (filesize: 19MB), using the free "QuickTime Player" application: