Spoiling The Youth With Ruby (Euruko 2010)

Spoiling The Youth With Ruby
EURUKO 2010
Karel Minařík

Karel Minařík
→ Independent web designer and developer („Have Ruby — Will Travel“)

→ Ruby, Rails, Git and CouchDB propagandista in .cz

→ Previously: Flash Developer; Art Director; Information Architect;… (see LinkedIn)

→ @karmiq at Twitter

→ karmi.cz

Spoiling the Youth With Ruby

I have spent couple of last years introducing spoiling
humanities students to with the basics of PR0GR4MM1NG.
(As a PhD student)

I’d like to share why and how I did it.

And what I myself have learned in the process.


I don’t know if I’m right.


But a bunch of n00bz was able to:

‣ Do simple quantitative text analysis (count number of pages, etc)
‣ Follow the development of a simple Wiki web application and
write code on their own
‣ Understand what $ curl ‐i ‐v http://example.com does
‣ And were quite enthusiastic about it

5 in 10 have „some experience“ with HTML
1 in 10 have „at last minimal experience“ with programming (PHP, C, …)


ΓΝΩΘΙ ΣΕΑΥΤΟN

Socrates

Socrates is guilty of spoling the youth (ἀδικεῖν τούϛ τε νέουϛ
διαφθείροντα) and not acknowledging the gods that the city

does, but some other new divinities (ἓτερα δὲ δαιμόνια καινά).

— Plato, Apology, 24b9


Some of our city DAIMONIA:

Students should learn C or Java or Lisp…
Web is for hobbyists…
You should write your own implementation of quick sort…
Project management is for „managers“…
UML is mightier than Zeus…
Design patterns are mightier than UML…
Test-driven development is some other new divinity…
Ruby on Rails is some other new divinity…
NoSQL databases are some other new divinities…
(etc ad nauseam)


Programming is
a specific way of thinking.


1 Why Teach Programming (to non-programmers)?


„To use a tool on a computer, you need do little more than
point and click; to create a tool, you must understand the
arcane art of computer programming“

— John Maeda, Creative Code


Literacy
(reading and writing)


Literacy

To most of my students, this:

File.read('pride_and_prejudice.txt').
split(' ').
sort.
uniq

is an ultimate, OMG this is soooooo cool hack

Although it really does not „work“ that well. That’s part of the explanation.


2 Ruby as an „Ideal” Programming Language?


There are only two hard things in Computer Science:
cache invalidation and naming things.
— Phil Karlton


The limits of my language mean the limits of my world
(Die Grenzen meiner Sprache bedeuten die Grenzen meiner Welt)

— Ludwig Wittgenstein, Tractatus Logico-Philosophicus 5.6


Ruby as an „Ideal” Programming Language?

We use Ruby because it’s…
Expressive
Flexible and dynamic
Not tied to a specific paradigm
Well designed (cf. Enumerable)
Powerful
(etc ad nauseam)


All those reasons are valid
for didactic purposes as well.



Of course… not only Ruby…



www.headfirstlabs.com/books/hfprog/


www.ericschmiedl.com/hacks/large-256.html

http://mit.edu/6.01
http://news.ycombinator.com/item?id=530605


5.times do
print "Hello. "
end



Let’s start with the basics...


An algorithm is a sequence of well defined and
finite instructions. It starts from an initial state
and terminates in an end state.
— Wikipedia


Algorithms and kitchen recipes

1. Pour oil in the pan
2. Light the gas
3. Take some eggs
4. ...


SIMPLE ALGORITHM EXAMPLE

Finding the largest number from unordered list

1. Let’s assume, that the first number in the list is the largest.

2. Let’s look on every other number in the list, in succession. If it’s larger
then previous number, let’s write it down.

3. When we have stepped through all the numbers, the last number
written down is the largest one.

http://en.wikipedia.org/wiki/Algorithm#Example Spoiling the Youth With Ruby


FORMAL DESCRIPTION IN ENGLISH

Input: A non‐empty list of numbers L
Output: The largest number in the list L

largest ← L0
for each item in the list L≥1, do
if the item > largest, then
largest ← the item
return largest



DESCRIPTION IN PROGRAMMING LANGUAGE C
1 #include <stdio.h>
2 #define SIZE 11
3 int main()
4 {
5   int input[SIZE] = {1, 5, 3, 95, 43, 56, 32, 90, 2, 4, 19};
6   int largest = input[0];
7   int i;
8   for (i = 1; i < SIZE; i++) {
9     if (input[i] > largest)
10       largest = input[i];
11   }
12   printf("Largest number is: %dn", largest);
13   return 0;
14 }



DESCRIPTION IN PROGRAMMING LANGUAGE Java
1 class MaxApp {
2   public static void main (String args[]) {
3     int[] input = {1, 5, 3, 95, 43, 56, 32, 90, 2, 4, 19};
4     int largest = input[0];
5     for (int i = 0; i < input.length; i++) {
6       if (input[i] > largest)
7         largest = input[i];
8     }
9     System.out.println("Largest number is: " + largest + "n");
10   }
11 }



DESCRIPTION IN PROGRAMMING LANGUAGE Ruby
1 input = [1, 5, 3, 95, 43, 56, 32, 90, 2, 4, 19]
2 largest = input.first
3 input.each do |i|
4 largest = i if i > largest
5 end
6 print "Largest number is: #{largest} n"



1 input = [1, 5, 3, 95, 43, 56, 32, 90, 2, 4, 19]
2 largest = input.first
3 input.each do |i|
4 largest = i if i > largest
5 end
6 print "Largest number is: #{largest} n"

largest ← L0
for each item in the list L≥1, do
if the item > largest, then
largest ← the item
return largest


What can we explain with this example?
‣ Input / Output
‣ Variable
‣ Basic composite data type: an array (a list of items)
‣ Iterating over collection
‣ Block syntax
‣ Conditions
# find_largest_number.rb
‣ String interpolation input = [3, 6, 9, 1]
largest = input.shift
input.each do |i|
largest = i if i > largest
end
print "Largest number is: #{largest} n"


That’s... well, basic...


BUT, YOU CAN EXPLAIN ALSO…

The concept of a function (method)…
  # Function definition:
  def max(input)
    input.each do |i|
    end
    return largest
  end

  # Usage:
  puts max( [3, 6, 9, 1] )
  # => 9



… the concept of polymorphy
def max(*input)
  input.each do |i|
  end
  return largest
end

# Usage
puts max( 4, 3, 1 )
puts max( 'lorem', 'ipsum', 'dolor' )
puts max( Time.mktime(2010, 1, 1),
          Time.now,
          Time.mktime(1970, 1, 1) )

puts max( Time.now, 999 ) #=> (ArgumentError: comparison of Fixnum with Time failed)



… that you’re doing it wrong — most of the time :)

# Enumerable#max
puts [3, 6, 9, 1].max


WHAT I HAVE LEARNED

Pick an example and stick with it
Switching contexts is distracting
What’s the difference between “ and ‘ quote?
What does the @ mean in a @variable ?
„OMG what is a class and an object?“


Interactive Ruby console at http://tryruby.org

"hello".reverse

[1, 14, 7, 3].max

["banana", "lemon", "ananas"].size
["banana", "lemon", "ananas"].sort
["banana", "lemon", "ananas"].sort.last
["banana", "lemon", "ananas"].sort.last.capitalize

5.times do
print "Hello. "
end


Great „one-click“ installer for Windows


Great resources, available for free

www.pine.fm/LearnToProgram (first edition)

Like, tooootaly excited!

Why’s (Poignant) Guide To Ruby

Ruby will grow with you („The Evolution of a Ruby Programmer“)

1 def sum(list)
total = 0
4 def sum(list)
total = 0
for i in 0..list.size-1 list.each{|i| total += i}
total = total + list[i] total
end end
total
end 5 def sum(list)
list.inject(0){|a,b| a+b}
2 def sum(list) end
total = 0
list.each do |item| 6 class Array
total += item def sum
end inject{|a,b| a+b}
total end
end end

3 def test_sum_empty
sum([]) == 0
7 describe "Enumerable objects should sum themselve

end it 'should sum arrays of floats' do
[1.0, 2.0, 3.0].sum.should == 6.0
# ... end

# ...
end

# ...

www.entish.org/wordpress/?p=707 Spoiling the Youth With Ruby

WHAT I HAVE LEARNED

If you’re teaching/training, try to learn
something you’re really bad at.
‣ Playing a musical instrument
‣ Drawing
‣ Dancing
‣ Martial arts

‣ …

It gives you the beginner’s perspective


3 Web as a Platform


20 09

www.shoooes.net

20 09

R.I.P. www.shoooes.net

But wait! Almost all of us are doing
web applications today.


Why web is a great platform?
Transparent: view-source all the way
Simple to understand
Simple and free development tools
Low barrier of entry
Extensive documentation
Rich platform (HTML5, „jQuery“, …)
Advanced development platforms (Rails, Django, …)
Ubiquitous
(etc ad nauseam)


CODED LIVE IN CLASS, THEN CLEANED UP AND PUT ON GITHUB

http://github.com/stunome/kiwi/

Why a Wiki?

Well known and understood piece of software with minimal
and well defined feature set (www.c2.com/cgi/wiki?WikiPrinciples)

Used on a daily basis (Wikipedia)

Feature set could be expanded based on individual skills


20 10

Sinatra.rb

www.sinatrarb.com Spoiling the Youth With Ruby

Sinatra.rb

Why choose Sinatra?
Expose HTTP! GET / → get("/") { ... }

Simple to install and run $ ruby myapp.rb

Simple to write „Hello World“ applications


Expose HTTP

$ curl --include --verbose http://www.example.com

* About to connect() to example.com port 80 (#0)
* Trying 192.0.32.10... connected
* Connected to example.com (192.0.32.10) port 80 (#0)
> GET / HTTP/1.1
...
< HTTP/1.1 200 OK
...
<
<HTML>
<HEAD>
<TITLE>Example Web Page</TITLE>
...
* Closing connection #0


Expose HTTP

# my_first_web_application.rb

require 'rubygems'
require 'sinatra'

get '/' do
"Hello, World!"
end

get '/time' do
Time.now.to_s
end


First „real code“ — saving pages

.gitignore       |    2 ++
application.rb   |   22 ++++++++++++++++++++++
views/form.erb   |    9 +++++++++
views/layout.erb |   12 ++++++++++++
4 files changed, 45 insertions(+), 0 deletions(‐)

http://github.com/stunome/kiwi/commit/33fb87 Spoiling the Youth With Ruby

Refactoring code to OOP (Page class)

application.rb | 4 +++‐
kiwi.rb | 7 +++++++
2 files changed, 10 insertions(+), 1 deletions(‐)

http://github.com/stunome/kiwi/commit/33fb87 Spoiling the Youth With Ruby

Teaching real-world processes and tools

www.pivotaltracker.com/projects/74202

Teaching real-world processes and tools

http://github.com/stunome/kiwi/

The difference between theory and practice
is bigger in practice then in theory.
(Jan L. A. van de Snepscheut or Yogi Berra, paraphrase)


What I had no time to cover (alas)

Automated testing and test-driven development
Cucumber
Deployment (Heroku.com)


What would be great to have

A common curriculum for teaching Ruby
(for inspiration, adaptation, discussion, …)

Code shared on GitHub

TeachingRuby (RailsBridge) (http://teachingkids.railsbridge.org)

Try Camping (http://github.com/judofyr/try-camping)

http://testfirst.org ?


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