This document discusses the history of computing and programming languages. It notes that many revolutionary ideas from the past are not yet common, such as treating code as objects and dynamic programs that can change as they run. The document advocates learning from the past by reading seminal works and learning languages like Lisp, Smalltalk, and Self to challenge current assumptions. Understanding our history can help us avoid reinventing solutions and using better approaches.

1. agile software development & services
Avoiding to re-invent the
flat tire
Hernán Wilkinson
Twitter: @HernanWilkinson
www.10pines.com

2. Alan Kay
“Our profession is like a pop culture”
…
“We don’t know our history”

3. The world “we live” in … ?

4. The world “we live” in … ?

5. The world “we live” in … ?

6. The world “we live” in … ?

7. Bret Victor - Thinking the unthinkable

8. How do we think about computing?
How do we think about its tools?

9. Computing
Alan Turing Alonzo Church

10. Computing
Machine vs. Algebra

11. Programming Languages
Algol-60, C, C++,
Java, C#...
Lisp, Smalltalk, Scheme, Self,
Ruby, Clojure…

12. Lisp
 Data = Code
 Lambda Functions
 Jit
 GC (Reference Counting)
 Meta-Circularity!!

13. Year?

14. Video
Sketchpad

15. Sketchpad
Ivan Sutherland
Visual Programming
Constrains Oriented

16. Year?

17. Simula 67
 Software as a Model!
 Organization of Knowledge
 History tip:
 Goto Considered Harmfull – 68
 Structured Programming – 71
(using Simula 67 as prog. lang.!!)

18. Video
Mother all Demos

19. The mother of all demos
Douglas Engelbart
Human Augmentation
Mouse
Direct Manipulation

20. Year?

21. Smalltalk
 Xerox Parc - LRG
Alan Kay
Dan Ingalls
Adele Goldberg

22. Smalltalk
Lisp
Simula 67
Flex Machine
DynaBook
Augment Children
Comprehention
Smalltalk
(72,74,76,78,80)
GUI - IDE
Object Oriented
VM
http://www.youtube.com/watch?v=AuXCc7WSczM

23. Alan Kay
"The best way to predict the future is to invent
it"
"I invented the term Object-Oriented and I can
tell you I did not have C++ in mind.“
"Java and C++ make you think that the new
ideas are like the old ones. Java is the most
distressing thing to hit computing since MS-
DOS.“
http://video.google.com/videoplay?docid=-
2950949730059754521
Smalltalk

24. Video
Smalltalk Examples

25. Video
Steve Jobs - Parc

26. Scheme

27. Closure
Lambda: The Ultimate …
(http://library.readscheme.org/page1.html)

28. Year?

29. Self
 David Ungar – Generation GC, PIC, etc.
 Randall Smith

30. What do they all have in common?
Revolutionary
Computer as a tool to augment human
understanding
Direct manipulation/Imm. Feedback
Simplicity
Consistency
Concretenees

31. Let’s see some stuff that is not
common YET, even thought it
is old… 

32. Current Problems – Example 1
We don’t see code as objects

33. List<Customer> selectedCustomers = new
ArrayList<Customer> ();
for (Customer customer: customers)
if (customer.nameStarsWith(“H”))
selectedCustomers.add (customer);
return selectedCustomers;
Looking for customers starting with H

34. List<Customer> selectedCustomers = new
ArrayList<Customer> ();
for (Customer customer: customers)
if (customer.nameStarsWith(“H”))
selectedCustomers.add (customer);
return selectedCustomers;
List<Account> selectedAccounts = new ArrayList<Account>
();
for (Account account: accounts)
if (account.isOverdraw())
selectedAccounts.add(account);
return selectedAccount;
Looking for overdraw accounts

35. List<Customer> selectedCustomers = new
ArrayList<Customer> ();
for (Customer customer: customers)
if (customer.nameStarsWith(“H”))
selectedCustomers.add (customer);
return selectedCustomers;
List<Account> selectedAccounts = new ArrayList<Account>
();
for (Account account: accounts)
if (account.isOverdraw())
selectedAccounts.add(account);
return selectedAccount;
WHAT’S THE PROBLEM!!??

36. List<Customer> selectedCustomers = new
ArrayList<Customer> (…);
for (Customer customer: customers)
if (customer.nameStarsWith(“H”))
selectedCustomers.add (customer);
return selectedCustomers;
List<Account> selectedAccounts = new ArrayList<Account>
();
for (Account account: accounts)
if (account.isOverdraw())
selectedAccounts.add(account);
return selectedAccount;
We have repeated code!

37. How to remove “repeated code”
 Copy the repeated code to “some
place” (method, class, etc)
 Parameterize what changes
 NAME IT!!

38. Copy repeated code
List<Customer> selectedCustomers =
new ArrayList<Customer> ();
for (Customer customer: customers)
if
(customer.nameStarsWith(“H”))
selectedCustomers.add(customer);
return selectedCustomers;
List<Account> selectedAccounts = new
ArrayList<Account> ();
for (Account account: accounts)
if (account.isOverdraw())
selectedAccounts.add(account);
return selectedAccount;
class Collection<T> {
public Collection<T> <<NAME>> {
List<T> selected = new ArrayList<T> ();
for (T anObject: this)
if ( )
selected.add (anObject);
return selected: }

39. Parameterize what changes
List<Customer> selectedCustomers = new ArrayList<Customer> ();
for (Customer customer: customers)
if (customer.nameStarsWith(“H”))
selectedCustomers.add (customer);
return selectedCustomers;
List<Account> selectedAccounts = new ArrayList<Account> ();
for (Account account: accounts)
if (account.isOverdraw())
selectedAccounts.add(account);
return selectedAccount;
How do we do it?

40. We need an abstraction to represent
code!
(remember, code is not text!)
closure…

41. Parameterize…
class Collection<T> {
public Collection<T> <<NAME>> (Closure aClosure) {
List<T> selected = new ArrayList<T> ();
for (T anObject: this)
if (aClosure.value(anObject) )
selected.add (anObject);
return selected:}
List<Customer> selectedCustomers =
new ArrayList<Customer> ();
for (Customer customer: customers)
if
(customer.nameStarsWith(“H”))
selectedCustomers.add(customer);
return selectedCustomers;
List<Account> selectedAccounts = new
ArrayList<Account> ();
for (Account account: accounts)
if (account.isOverdraw())
selectedAccounts.add(account);
return selectedAccount;

42. NAME IT!
class Collection<T> {
public Collection<T> select (Closure aClosure) {
List<T> selected = new ArrayList<T> ();
for (T anObject: this)
if (aClosure.value(anObject) )
selected.add (anObject);
return selected:}
The most difficult
part because it
means that we
understood the
repeated code
meaning
List<Customer> selectedCustomers =
new ArrayList<Customer> ();
for (Customer customer: customers)
if
(customer.nameStarsWith(“H”))
selectedCustomers.add(customer);
return selectedCustomers;
List<Account> selectedAccounts = new
ArrayList<Account> ();
for (Account account: accounts)
if (account.isOverdraw())
selectedAccounts.add(account);
return selectedAccount;

43. List<Customer> selectedCustomers = new ArrayList<Customer> ();
for (Customer customer: customers)
if (customer.nameStarsWith(“H”))
selectedCustomers.add (customer);
return selectedCustomers;
List<Account> selectedAccounts = new ArrayList<Account> ();
for (Account account: accounts)
if (account.isOverdraw())
selectedAccounts.add(account);
return selectedAccount;
cutomers.select( customer => customer.nameStartsWith(“H”) )
accounts.select( account => account.isOverdraw() )

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

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

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

47. 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?

48. Current Problems – Example 2
Programs don’t change while running

49. Current Problems – Example 3
We still think that code is text

50. Current Problems – Example 4
We don’t use objects all the way down
We still using text as main communication
media

51. So… Why is it not
common???

52. The right question is:
So… Why is it not common
YET???

53. Conclusion
If you don’t want to re-invent the
wheel…
If you don’t want to use a flat
tire…

54. We have to learn our history
We have to be open to challenge the
status quo
Do not accept new things as better
things just because they are new
Do not be an uncritical consumer!

55. Must Read
 The early History of Smalltalk
 Lambda the Ultimate …
 Structure and Interpreteation of Computer
Programs
 Smalltalk 80
 Lisp 1.5 user manual
 Self papers
 ACM Preccedings on HOLP
 …

56. Must Watch
Alan Kay on:
Computer Revolution has not happened yet
Normal Considered Harmfull
The Dynabook: Past, Present and Future
… and more!
Structure and Interpreteation of
Computer Programs
Bret Victor videos
Self movie

57. Must Learn
Lisp/Scheme (Dr.Racket/Clojure) not
cdr, car, etc. but apply/eval
Smalltalk
Self

58. Questions?

59. agile software development & services
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