DirtyInformation

A is for Abbrev

I hope that this is only the first in a set of posts that are to make an intriguing right of passage through the ABCs of the core and standard libraries.

‘A’ begins the alphabet and it would be so easy to start out with Ruby’s Array. Everyone knows there are many amazing ways to traverse, and manipulate Ruby’s array, but we want to grow in our knowledge. Instead of Array we set our sites on a very small Module, Abbrev.

Weighing in at only 131 lines there isn’t much to talk about. Once we put it on a comment diet Abbrev has a mere 44 lines of code. These 44 lines create only two methods.

The first method is the module function Abbrev.abbrev. This method can take two arguments. The first argument is an array of strings. The second is an optional argument, but we will get back to that in a moment. For now we will concentrate on the required argument. When passing in an array of strings Abbrev.abbrev returns a hash of, get this, abbreviations. The abbreviations are created by taking the beginning of each word until it clashes with another abbreviation.

  require "abbrev"
  require "pp" #for your reading pleasure
  pp Abbrev.abbrev(%w[aardvark arron amos dog])
  {"aardvark"=>"aardvark",
   "aardvar"=>"aardvark",
   "aardva"=>"aardvark",
   "aardv"=>"aardvark",
   "aard"=>"aardvark",
   "aar"=>"aardvark",
   "aa"=>"aardvark",
   "arron"=>"arron",
   "arro"=>"arron",
   "arr"=>"arron",
   "ar"=>"arron",
   "amos"=>"amos",
   "amo"=>"amos",
   "am"=>"amos",
   "dog"=>"dog",
   "do"=>"dog",
   "d"=>"dog"}

Now that we have hit the pinnacle of what ruby can do, and still scale, it is time to move on to the optional argument. The optional argument is a pattern that is used to match against the abbreviations. It can be a string or a regular expression. If a string is passed it is treated as a begins with when matching against the abbreviations.

  pp Abbrev.abbrev(%w[aardvark arron amos dog], /ar/)
  {"aardvark"=>"aardvark",
    "aardvar"=>"aardvark",
    "aardva"=>"aardvark",
    "aardv"=>"aardvark",
    "aard"=>"aardvark",
    "aar"=>"aardvark",
    "arron"=>"arron",
    "arro"=>"arron",
    "arr"=>"arron",
    "ar"=>"arron"}

I haven’t found a great use for the pattern argument. If you have any ideas let me know, and I will add them to the bottom of the article. Even better, make a pull request to the blog. I like to use the Abbrev when creating command line utilities that take subcommands. You can then check the subcommands against the hash output of Abbrev.abbrev. Then your power users have shortcuts. You might notice this with the rails command. rails generate vs rails g.

Next time your creating a command line utility, or accepting commands in your own MUD, reach for Abbrev like a boss.

I almost forgot, the second method. When you require abbrev an extension is added to array. Array.abbrev that takes an optional pattern. This in turn calls Abbrev.abbrev(self, pattern).

The Past

• Testing Named Agents 03 Feb 2017
• Two Duplication Refactorings in Elixir 18 Jan 2017
• B is for BigDecimal 24 Sep 2014
• A is for Abbrev 02 Sep 2014
• Missed Chances 15 Aug 2014
• Style Guides are Failures 15 Jun 2014
• What is BDD anyway? 15 Apr 2014
• An Agile Contract 31 Mar 2014
• What Do I Want 23 Mar 2014
• Just the Tip 16 Mar 2014
• Important Partnerships 11 Mar 2014
• Lost in Translation 03 Mar 2014
• Story Splitting Revisited 23 Feb 2014
• Let your yes be yes and your no be no 16 Feb 2014
• Lethal Injection 09 Feb 2014
• Smaller is Better 02 Feb 2014
• A Second Time 26 Jan 2014
• Introspective 20 Jan 2014
• Self Reflection for the Win 06 Dec 2013
• Why? Why? Why? 30 Sep 2013
• A New Gig 18 Sep 2013
• Exceptional Comments 15 Jun 2013
• Role Objects in Acceptance Tests 30 Apr 2013
• Open Closed Ruby Woes 28 Apr 2013
• Write Something 12 Apr 2013
• A Great Cast of Characters 06 Mar 2012
• When is the Release Party? 19 Aug 2011
• Single Responsibilty, How Did I Forget You 12 Apr 2011
• Change Classes not Styles 05 Nov 2010
• My MongoDB Cookbook Recipe 20 Jul 2010
• Agile Says What? 05 Nov 2009
• Inject & Me - BFFs 07 Sep 2008