Regional Scrum Gathering Ecuador 2015 Key Note

1. agile software development & services
Los Lenguajes de
Programación y su Impacto
en el Pensamiento
Hernán Wilkinson
Twitter: @HernanWilkinson
Blog: objectmodels.blogspot.com
www.10pines.com

2. The world “we live” in … ?

3. The world “we live” in … ?

4. The world “we live” in … ?

5. The world “we live” in … ?

6. Bret Victor - Thinking the unthinkable

7. Language <-> Thinking

8. What we can not talk about…
we can not think about
(or it is difficult...)

9. Do not Insist on English

10. Aimara: Pasado y Futuro
(nayra) (qhipa)

12. What is the relationship with
Programming Languages?
(K. Iverson: “Notation as a tool of thought”
1979 ACM Turing Award)

13. If a programming
language does not
allow me to “TALK”
(write) about certain
things
…
Then I can not THINK
about certain
solutions

14. Let’s see
Li st <Cust omer > sel ect edCust omer s = new Ar r ayLi st <Cust omer > ( ) ;
f or ( Cust omer cust omer : cust omer s)
i f ( cust omer . nameSt ar sWi t h( “ H” ) )
sel ect edCust omer s. add ( cust omer ) ;
r et ur n sel ect edCust omer s;

15. Let’s see
Li st <Cust omer > sel ect edCust omer s = new Ar r ayLi st <Cust omer > ( ) ;
f or ( Cust omer cust omer : cust omer s)
i f ( cust omer . nameSt ar sWi t h( “ H” ) )
sel ect edCust omer s. add ( cust omer ) ;
r et ur n sel ect edCust omer s;
Li st <Account > sel ect edAccount s = new Ar r ayLi st <Account > ( ) ;
f or ( Account account : account s)
i f ( account . i sOver dr aw( ) )
sel ect edAccount s. add( account ) ;
r et ur n sel ect edAccount ;

16. Let’s see
Li st <Cust omer > sel ect edCust omer s = new Ar r ayLi st <Cust omer > ( ) ;
f or ( Cust omer cust omer : cust omer s)
i f ( cust omer . nameSt ar sWi t h( “ H” ) )
sel ect edCust omer s. add ( cust omer ) ;
r et ur n sel ect edCust omer s;
Li st <Account > sel ect edAccount s = new Ar r ayLi st <Account > ( ) ;
f or ( Account account : account s)
i f ( account . i sOver dr aw( ) )
sel ect edAccount s. add( account ) ;
r et ur n sel ect edAccount ;
What is the problem?

17. We have repeated code!
Li st <Cust omer > sel ect edCust omer s = new Ar r ayLi st <Cust omer > ( ) ;
f or ( Cust omer cust omer : cust omers)
i f ( cust omer. nameSt arsWi t h(“H”) )
sel ect edCust omer s. add ( cust omer ) ;
r et ur n sel ect edCust omer s;
Li st <Account > sel ect edAccount s = new Ar r ayLi st <Account > ( ) ;
f or ( Account account : account s)
i f ( account . i sOverdraw() )
sel ect edAccount s. add( account ) ;
r et ur n sel ect edAccount ;

18. Code != Text

19. How do we remove it?

20. Technique:
1. “Contextualize-Copy” the repeated
code to some “place”
2. Parameterize what changes
3. NAME IT!!!
4. Use it :-)

21. cl ass Col l ect i on<T> {
publ i c Col l ect i on<T> <<NAME>> ( ?) {
Li st <T> sel ect ed = new Ar r ayLi st <T> ( ) ;
f or ( T anObj ect : t hi s )
i f ( )
sel ect ed. add ( anObj ect ) ;
r et ur n sel ect ed: }
this
Copy the repeated code to some place
Li st <Cust omer > sel ect edCust omer s =
new Ar r ayLi st <Cust omer > ( ) ;
f or ( Cust omer cust omer : cust omers)
i f ( cust omer. nameSt arsWi t h(“H”) )
sel ect edCust omer s. add( cust omer ) ;
r et ur n sel ect edCust omer s;
Li st <Account > sel ect edAccount s = new
Ar r ayLi st <Account > ( ) ;
f or ( Account account : account s)
i f ( account . i sOverdraw() )
sel ect edAccount s. add( account ) ;
r et ur n sel ect edAccount ;

22. Parameterize what changes
Li st <Cust omer > sel ect edCust omer s = new Ar r ayLi st <Cust omer > ( ) ;
f or ( Cust omer cust omer : cust omer s)
i f ( cust omer. nameSt arsWi t h(“H”) )
sel ect edCust omer s. add ( cust omer ) ;
r et ur n sel ect edCust omer s;
Li st <Account > sel ect edAccount s = new Ar r ayLi st <Account > ( ) ;
f or ( Account account : account s)
i f ( account . i sOverdraw() )
sel ect edAccount s. add( account ) ;
r et ur n sel ect edAccount ;
How do we do it?

23. An object that represents “code”

24. cl ass Col l ect i on<T> {
publ i c Col l ect i on<T> <<NAME>> ( Cl osure aCl osure) {
Li st <T> sel ect ed = new Ar r ayLi st <T> ( ) ;
f or ( T anObj ect : t hi s )
i f ( )
sel ect ed. add ( anObj ect ) ;
r et ur n sel ect ed: }
this
Copy the repeated code to some place
Li st <Cust omer > sel ect edCust omer s =
new Ar r ayLi st <Cust omer > ( ) ;
f or ( Cust omer cust omer : cust omers)
i f ( cust omer. nameSt arsWi t h(“H”) )
sel ect edCust omer s. add( cust omer ) ;
r et ur n sel ect edCust omer s;
Li st <Account > sel ect edAccount s = new
Ar r ayLi st <Account > ( ) ;
f or ( Account account : account s)
i f ( account . i sOverdraw() )
sel ect edAccount s. add( account ) ;
r et ur n sel ect edAccount ;
aClosure.execute(anObject)

25. cl ass Col l ect i on<T> {
publ i c Col l ect i on<T> sel ect ( Cl osure aCl osure) {
Li st <T> sel ect ed = new Ar r ayLi st <T> ( ) ;
f or ( T anObj ect : t hi s )
i f ( )
sel ect ed. add ( anObj ect ) ;
r et ur n sel ect ed: }
self
NAME IT!
Li st <Cust omer > sel ect edCust omer s =
new Ar r ayLi st <Cust omer > ( ) ;
f or ( Cust omer cust omer : cust omers)
i f ( cust omer. nameSt arsWi t h(“H”) )
sel ect edCust omer s. add( cust omer ) ;
r et ur n sel ect edCust omer s;
Li st <Account > sel ect edAccount s = new
Ar r ayLi st <Account > ( ) ;
f or ( Account account : account s)
i f ( account . i sOverdraw() )
sel ect edAccount s. add( account ) ;
r et ur n sel ect edAccount ;
aClosure.execute(anObject)
The most difficult
part because it
means that we
understood the
repeated code
meaning

26. Li st <Cust omer > sel ect edCust omer s = new Ar r ayLi st <Cust omer > ( ) ;
f or ( Cust omer cust omer : cust omer s)
i f ( cust omer . nameSt ar sWi t h( “ H” ) )
sel ect edCust omer s. add ( cust omer ) ;
r et ur n sel ect edCust omer s;
Li st <Account > sel ect edAccount s = new Ar r ayLi st <Account > ( ) ;
f or ( Account account : account s)
i f ( account . i sOver dr aw( ) )
sel ect edAccount s. add( account ) ;
r et ur n sel ect edAccount ;
cut omer s. sel ect ( cust omer - > cust omer . nameSt ar t sWi t h( “ H” ) )
account s. sel ect ( account - > account . i sOver dr aw( ) )

27. What did we gain?
1. Few words  Simplicity, Easier to
understand, read, remember, etc.
Less bugs!
2. We created a new “abstraction”:
select (filter in Java 8)
3. … and we removed duplicated
code!!

28. Now… let’s do some reflection

29. 1. Because we are use to that code (is
the programming language the
problem or us?)
2. Because there is no “concept” to
remove it
Why didn’t we see the
“duplicated code”

30. Why didn’t we came with a
solution?
1. Because the programming language
does not provide us with a “concept”
to think about a solution!

31. …and much much
more….
Imagine how your
designs would be if
you could use closures
You can create your own control flow
“sintax”
Further reading: LAMBDA The Ultimate…

32. Hamming / Closure
If there are certain objects that can not be
created in some languages …
… and given the solutions provided by some
programming languages…
The statement: “There are design solutions
that are unthinkable in some
programming languages”
¿Does it surprise you?

33. Meta-Conclusion
Object = ¿Data + Code?

34. Meta-Conclusion
Object = ¿Data + Code?
If you think so, you don´t understand OO yet

35. Meta-Conclusion
Data is an Object
Code is an Object
An Object is a “superior”
concept that unifies data and
code

36. What is the problem?

37. No If!

38. Now… let’s do some reflection

39. Why did we not see the
“polymorphic message”?

Because 'if' as a reserved word is a
“primitive construction”, there is
nothing behind it

Therefore it does not make us think in
polymorphism

40. If as a message

42. A programming language is
its creator's state of
knowledge

43. timeToRun

44. timeToRun

45. timeToRun

46. timeToRun

47. timeToRun

48. timeToRun

49. timeToRun

50. timeToRun

51. Extending a Language!

52. How can we add specific
behavior to an object?
Let's see an example

53. Now… let’s do some reflection
1. What are the solutions
we lack due to limited
meta programming?
2. What do we loose if we
do not have a meta-
circular language?

54. How do we learn a new word?

55. Do we:
1. Stop our brain
2. “edit" a new definition in our
dictionary
3. “Compile” the new definition
4. Restart our brain?

56. NO!!
Why do we have to do it with our
programs?

57. Can our programs “change while
running”?
Can our programs “learn” as we learn?

58. Yes, they can!... If they are
METACIRCULAR
Apply
Eval

59. If we don’t have meta-circular
languages, then we can not think
about solutions that are natural in
our daily lives!!

60. Let’s think again…
Are these concepts new?

61. Lisp
John McCarthy
Alan Kay
“We must know our history
if we don’t want to reinvent
… not only the tire, but a
a flat tire”

62. Conclusions
 Do not accept languages without
Closures
 Do not accept languages without
good meta-programming
 Create your own extensions!
 Liberate yourself from the
programming language and
frameworks

63. Conclusions
 Learn other programming
languages
Lisp/Scheme
Smalltalk
Forth and more...
 Learn our history

64. "The Humble Programmer”
E. Dijkstra
“The tools we are trying to use
and the language or notation
we are using to express or
record our thoughts, are the
major factors determining
what we can think or express
at all!"

65. Questions?

66. agile software development & services
Muchas gracias!
info@10pines.com
www.10Pines.com
twitter: @10Pines
Argentina
Tel.: +54 (11) 6091-3125
Alem 693, 5B
(1001) Buenos Aires