Reading GOOS (VI)

These are the links mentioned in this week's conversation about the 7th chapter:

1. Posts and papers
   • Traits: Composable Units of Behaviour by Schärli et al
   • Shotgun Surgery
   • Refused Bequest
   • EncapsulatedCollection by Martin Fowler
2. Talks
   • Primitive obssesion and Value objects conversation between J. B. Rainsberger and Corey Haines (part 1)
   • Primitive obssesion and Value objects conversation between J. B. Rainsberger and Corey Haines (part 2)
3. Books
   • On Lisp by Paul Graham

Kata: Refactoring Tennis in Ruby

We practiced with the Refactoring Tennis kata in the last Barcelona Ruby meetup.

There were three different versions of the original code. I refactored the first one.

This is the original code:


First, I tried to refactor the code to the State Pattern as I did once before in C++. Then I realized checking the tests that the code was not meant to model a real tennis game. It's just focused in displaying the current score.

So I decided to try to separate the code that was keeping the tennis game score from the code that was displaying its score. I also wanted to be able to display the score in different languages.

This is the resulting code after the refactoring:


The TennisGame has two collaborators: the GameScore and the ScoreDisplayer.

The GameScore keeps track of the two Players in order to answer questions about the game score, whereas the ScoreDisplayer is in charge of displaying the score.

By default the ScoreDisplayer uses an English GameVocabulary, but the GameVocabulary can be injected through its accessor in order to display the score a different language (check the tests to see how the score is displayed in Spanish).

You can check the code and its tests in this GitHub repository.

I also committed after every tiny refactoring step so you can follow the process (especially the changes of mind I had and the dead-ends I found).

This kata was a great puzzle to practise and think.

I'd like to thank David Vrensk for his great work facilitating the kata and the interesting talk about Deliberate Practice that he gave before.

Kata: Bowling Game in Clojure

I've just done the Bowling Game Kata in Clojure.

These are the tests using Midje:


and this is the code:


I used a mix of TDD and REPL-driven development to solve it.

I commited the code after every passing test, every refactor and every major REPL spike.

If you want to follow the process, you can find the commits step by step here.

You can find the resulting code in GitHub.

Kata: Unconditional rock, paper, scissors in Ruby

Yesterday Álvaro García (@alvarobiz) and I paired working on a possible solution to the Unconditional rock, paper, scissors kata that I facilitated in the recent SCBCN14 event.

This is the last version of the tests so far:


And this is the last version of the code:


We managed to write the code without having to use conditionals in any moment.

You can follow the process if you like since we did commits after every passing test and every refactoring.

You can check the code in this GitHub repository.

As usual it was a pleasure to do pair programming with Álvaro.

Euler Project: Problem 1 in Haskell

This is my solution in Haskell to the first problem:

I used a list comprehension.

Another way using also a lambda to create a helper:



Bonus: Two ways to do the same in Clojure: