# Programmer Ping-Pong (#150)

**URL:** <https://www.ruby-forum.com/t/programmer-ping-pong-150/123771>\
**Category:** Ruby\
**Created:** [December 20, 2007, 2:38pm UTC](https://www.ruby-forum.com/t/programmer-ping-pong-150/123771 "2007-12-20T14:38:25Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![bbazzarrakk](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/47e85d/32.png) [@bbazzarrakk](https://www.ruby-forum.com/u/bbazzarrakk)\
**Post date:** [December 20, 2007, 2:38pm UTC](https://www.ruby-forum.com/t/programmer-ping-pong-150/123771/1 "2007-12-20T14:38:25Z")

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This quiz was definitely more about the process than what we produced.  
For the  
record though, I do feel what we produced was quite successful. We have  
built a  
full AVL Tree implementation in under a week. It may still have a bug  
or two we  
haven’t eliminated, but it’s certainly usable. Let me prove that to  
you.

Here is the start of an ordered Hash implementation I said would be  
possible  
with a working AVL tree. Unlike Ruby 1.9’s built-in Hash ordering, this  
class  
orders pairs by their key instead of their insertion order:

#!/usr/bin/env ruby -wKU

require “avl\_tree”

class KeyOrderedHash  
Pair = Struct.new(:key, :value) do  
def \<=\>(other)  
key \<=\> other.key  
end  
end

```
include Enumerable

def initialize
  @pairs = AVLTree.new
end

def [](key)
  @pairs[Pair.new(key)].value
end

def []=(key, value)
  @pairs << Pair.new(key, value)
end

def each
  @pairs.each { |pair| yield pair.to_a }
end

```

end

if **FILE** == $PROGRAM\_NAME  
require “pp”

```
names = KeyOrderedHash.new
%w[ Rob\ Biedenharn
    Adam\ Shelly
    James\ Koppel ].each_with_index do |name, i|
  names[name] = i
end
pp names.to_a
# >> [["Adam S.", 1], ["James K.", 2], ["Rob B.", 

```

0]]  
end

Note how the pairs here come out in key order, instead of the insertion  
order  
shown by their values.

The process was also pretty successful. Some felt email was a poor  
medium to  
conduct this kind of experiment and they were probably right. Rob  
Biedenharn  
came to our rescue though with two simple tools for embedding and  
extracting the  
code from an email. Together these two tools were under 40 lines of  
code and  
they helped a lot. Nice problem solving, Rob.

We did see quite a bit of forking early on, but in the end a single  
branch of  
the code seemed to dominate. Solvers were good about incorporating the  
changes  
of others though, so I didn’t really feel like this aspect affected the  
results  
much.

As of James K.'s first response, the code has gone through 15 rounds  
of  
revision, not counting forks. In that time, we generated right around  
500 lines  
of code including the tests. I was pretty impressed by all of that.

Obviously, the largest aspect of this quiz was the game of Test Driven  
Development. That too was interesting to watch unfold. Tests were  
edited,  
commented out, and reinstated all at various times during the exercise.  
This  
happens all the time in normal development of course, but it’s different  
when  
you are doing these things to someone else’s tests.

It’s my opinion that the testing got off track a bit early on when we  
tried to  
do height testing before we really had a height to test. A few early  
height  
tests eventually caused this method to crop up inside AVLTree:

```
# ...

def height
  (Math.log(@contents.size + 1) / Math.log(2)).round
end

# ...

```

While that does reflect accurate results for what we were trying to  
accomplish,  
it really doesn’t have anything to do with our tree. It just proves  
that we  
figured out the math. This is one place where I feel the concept of  
only-do-what’s-needed-to-pass-the-tests breaks down. This code just has  
to be  
rewritten at some point, so there’s not much benefit to bypassing a test  
with  
it, in my opinion.

Another area where we had trouble with the tests was in trying to  
measure the  
speed of something. None of us could come up with a great way to test  
for  
whether and insert operation was O(n) or O(log n) or something else  
entirely.  
One poster suggested that test driving algorithms wasn’t very effective  
and,  
while I’m not sure I fully agree with that, this is definitely one of  
the  
problem cases.

All in all though, the process was a big success and we produced great  
results.  
I encourage everyone to read through the quiz thread and see how our  
work  
evolved. Thanks for indulging me in my desires to try something a  
little  
different.

There will be no Ruby Q. this week in celebration of the Christmas  
holiday. I  
wish you all a Merry Christmas and I’ll talk to you again next week.

---

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**Author:** ![bbazzarrakk](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/47e85d/32.png) [@bbazzarrakk](https://www.ruby-forum.com/u/bbazzarrakk)\
**Post date:** [December 20, 2007, 4:49pm UTC](https://www.ruby-forum.com/t/programmer-ping-pong-150/123771/2 "2007-12-20T16:49:47Z")

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On 12/20/07, Ruby Q. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> As of James K.'s first response, the code has gone through 15 rounds of  
> revision, not counting forks.

## Should that be either last or latest? As far as I know, I was the first respondent.

Rick DeNatale

My blog on Ruby  
[http://talklikeaduck.denhaven2.com/](http://talklikeaduck.denhaven2.com/)

---

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**Author:** ![bbazzarrakk](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/47e85d/32.png) [@bbazzarrakk](https://www.ruby-forum.com/u/bbazzarrakk)\
**Post date:** [December 20, 2007, 5:05pm UTC](https://www.ruby-forum.com/t/programmer-ping-pong-150/123771/3 "2007-12-20T17:05:02Z")

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On Dec 20, 2007, at 9:48 AM, Rick DeNatale wrote:

> On 12/20/07, Ruby Q. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:
> 
> > As of James K.'s first response, the code has gone through 15  
> > rounds of  
> > revision, not counting forks.
> 
> Should that be either last or latest? As far as I know, I was the  
> first respondent.

Note the possessive: “James K.'s first response.”

James Edward G. II

---

<div class="post-metadata">

**Author:** ![bbazzarrakk](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/47e85d/32.png) [@bbazzarrakk](https://www.ruby-forum.com/u/bbazzarrakk)\
**Post date:** [December 20, 2007, 5:36pm UTC](https://www.ruby-forum.com/t/programmer-ping-pong-150/123771/4 "2007-12-20T17:36:07Z")

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On 2007-12-20, Ruby Q. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> This quiz was definitely more about the process than what we produced. For the  
> record though, I do feel what we produced was quite successful.

I loved this quiz, I had a lot of work to do this week so I missed out  
on the ending but I’d definitely love to see more quizzes like this.

---

<div class="post-metadata">

**Author:** ![bbazzarrakk](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/47e85d/32.png) [@bbazzarrakk](https://www.ruby-forum.com/u/bbazzarrakk)\
**Post date:** [December 20, 2007, 5:40pm UTC](https://www.ruby-forum.com/t/programmer-ping-pong-150/123771/5 "2007-12-20T17:40:14Z")

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On Dec 20, 2007, at 11:04 AM, James G. wrote:

> James Edward G. II

Rick, Read it without the word “first” and then think of future-  
proofing for another response (or two) from James K…

-Rob

Rob B. [http://agileconsultingllc.com](http://agileconsultingllc.com)  
removed\_email\_address@domain.invalid

---

<div class="post-metadata">

**Author:** ![bbazzarrakk](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/47e85d/32.png) [@bbazzarrakk](https://www.ruby-forum.com/u/bbazzarrakk)\
**Post date:** [December 28, 2007, 1:33am UTC](https://www.ruby-forum.com/t/programmer-ping-pong-150/123771/6 "2007-12-28T01:33:56Z")

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On Dec 20, 2007, at 7:36 AM, Ruby Q. wrote:

> There will be no Ruby Q. this week in celebration of the Christmas  
> holiday. I  
> wish you all a Merry Christmas and I’ll talk to you again next week.

The holiday and an unexpected illness are slowing me down folks. Give  
me one more week to recover and I promise to get the quiz back on its  
feet.

James Edward G. II