Talk at Smalltalks 2016 about how easy is in Smalltalk to create control flow structures and play with that.

1. agile software development & services
Augmenting Smalltalk
with your own Control
Flow Syntax
www.10pines.com
Hernán Wilkinson
Twitter: @HernanWilkinson
Blog: objectmodels.blogspot.com
www.10pines.com

2. In linguistics, syntax is the set of rules, principles, and
processes that govern the structure of sentences in a
given language, specifically word order. The term
syntax is also used to refer to the study of such
principles and processes. The goal of many
syntacticians is to discover the syntactic rules common
to all languages.
In mathematics, syntax refers to the rules governing the
behavior of mathematical systems, such as formal
languages used in logic. (See logical syntax.)
Syntax

3. In linguistics, grammar is the set of structural rules
governing the composition of clauses, phrases, and
words in any given natural language. The term refers
also to the study of such rules, and this field includes
morphology, syntax, and phonology, often
complemented by phonetics, semantics, and
pragmatics.
Grammar

4. How easy is to change the syntax?
How easy is to change the grammar?
Change

5. Complexity = essential + accidental
Complexity

6. Complexity = essential + accidental
Complexity
We can not reduce
this one

7. Complexity = essential + accidental
Complexity
We can not reduce
this one
We can definitely
reduce this one

8. Smalltalk Complexity

9. One day, in a typical PARC hallway bullsession, Ted
Kaehler, Dan Ingalls, and I were standing around
talking about programming languages. The subject of
power came up and the two of them wondered how
large a language one would have to make to get
great power. With as much panache as I could
muster, I asserted that you could define the "most
powerful language in the world" in "a page of
code." They said, "Put up or shut up."

11. “The biggest hit for me while at SAIL
in late '69 was to really understand
LISP. Of course, every student knew
about car, cdr, and cons, but … no one
had penetrated the mysteries of eval
and apply. I could hardly believe how
beautiful and wonderful the idea of
LISP was [McCarthy 1960]”

13. “… there were deep flaws in its
logical foundations. By this, I mean
that the pure language was supposed
to be based on functions, but its most
important components--such as
lambda expressions, quotes, and
conds--were not functions at all, and
instead were called special forms”

14. Closure

15. Closure
Lisp Lambda Functions
Algol-60 Block &
Lexicographic binding
Scheme Closure

21. “with full closures you can
avoid control flow syntax”

22. Smalltalk Syntax
object message
(and other minor stuff)

23. if

25. Closure

26. Does not
compile!

29. Example

30. (Ruby)

31. (Ruby)

33. while

34. Does not compile!

36. Closure

37. Closure
Boolean or Closure?

39. Example

41. exceptions

44. Closure
Closure

46. Implicit condition… why?Implicit condition… why?

48. In how many places is ZeroDevide handled?
In how many places is SubscriptOutOfBounds handled?

50. Resources

52. file will not close if an exception
signals before

56. Syntatically solved again

57. DSL

61. Conclusions
▶ Less syntax  more flexibility
▶ Less syntax  more grammar
▶ More grammar  easier to change,
to augment!
▶ Less syntax makes the language
yours!
▶ Don’t be afraid! Make your own
language!

62. Questions?
@hernanwilkinson
Hernan.wilkinson@10pines.com

63. agile software development & services
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