Affordances in Programming Languages

From Mountain West Ruby Conference 2014.

A good design communicates the intended use of an object. In the physical world, this communication is accomplished by “affordances”, as discussed by Donald Norman in “The Psychology of Everyday Things”.

Programming languages also have affordances, and they influence the kinds of solutions we develop. The more languages we know, the more we “expand our design space” so that we can come up with better solutions to the problems we face every day.

Transcript

1. 3/20/2014 Affordances http://localhost:9090/onepage 1/67 Affordances in Programming Languages Randy Coulman Principal Software Engineer http://randycoulman.com @randycoulman randycoulman
2. 3/20/2014 Affordances http://localhost:9090/onepage 2/67 Satu Kyröläinen ­ http://www.satukyrolainen.com/affordances/
3. 3/20/2014 Affordances http://localhost:9090/onepage 3/67 Satu Kyröläinen ­ http://www.satukyrolainen.com/affordances/
4. 3/20/2014 Affordances http://localhost:9090/onepage 4/67 Affordance A quality of an object or environment that allows someone to perform an action.
5. 3/20/2014 Affordances http://localhost:9090/onepage 5/67 Nicolas Nova ­ http://www.flickr.com/photos/nnova/2252222949/
6. 3/20/2014 Affordances http://localhost:9090/onepage 6/67 William Lindeke ­ http://tcsidewalks.blogspot.com/2009/06/signs­of­times­14.html
7. 3/20/2014 Affordances http://localhost:9090/onepage 7/67 Yoni Alter ­ http://www.yoniishappy.com/Tube­escalators
8. 3/20/2014 Affordances http://localhost:9090/onepage 8/67 Affordances and Software
9. 3/20/2014 Affordances http://localhost:9090/onepage 9/67 Amir Rajan (@amirrajan) Coding Out Loud ­ REST APIs series http://vimeo.com/channels/659338
10. 3/20/2014 Affordances http://localhost:9090/onepage 10/67 Example Points Smalltalk ­> Ruby
11. 3/20/2014 Affordances http://localhost:9090/onepage 11/67 c l a s s P o i n t d e f i n i t i a l i z e ( x , y ) @ x = x @ y = y e n d e n d P o i n t . n e w ( 3 , 4 )
12. 3/20/2014 Affordances http://localhost:9090/onepage 12/67 http://images.cryhavok.org/d/25562­2/Polar+and+Cartesian+Bears.jpg
13. 3/20/2014 Affordances http://localhost:9090/onepage 13/67 θ r sinθ r cosθ r x y http://upload.wikimedia.org/wikipedia/commons/7/78/Polar_to_cartesian.svg
14. 3/20/2014 Affordances http://localhost:9090/onepage 14/67 c l a s s P o i n t d e f i n i t i a l i z e ( x , y ) @ x = x @ y = y e n d e n d P o i n t . n e w ( 3 , 4 )
15. 3/20/2014 Affordances http://localhost:9090/onepage 15/67 P o i n t c l a s s > > x : a n X y : a Y ^ s e l f n e w i n i t i a l i z e X : a n X y : a Y P o i n t > > i n i t i a l i z e X : a n X y : a Y x : = a n X . y : = a Y P o i n t x : 3 y : 4
16. 3/20/2014 Affordances http://localhost:9090/onepage 16/67 P o i n t c l a s s > > r : r a d i u s t h e t a : a n g l e I n R a d i a n s ^ s e l f x : r a d i u s * a n g l e I n R a d i a n s c o s y : r a d i u s * a n g l e I n R a d i a n s s i n P o i n t r : 5 t h e t a : 0 . 9 2 7 2 9 5
17. 3/20/2014 Affordances http://localhost:9090/onepage 17/67 Affordance Named Constructors
18. 3/20/2014 Affordances http://localhost:9090/onepage 18/67 c l a s s P o i n t d e f s e l f . x y ( x , y ) n e w ( x , y ) e n d d e f s e l f . p o l a r ( r , t h e t a ) x y ( r * M a t h . c o s ( t h e t a ) , r * M a t h . s i n ( t h e t a ) ) e n d p r i v a t e _ c l a s s _ m e t h o d : n e w # . . . r e s t s a m e a s b e f o r e e n d P o i n t . x y ( 3 , 4 ) P o i n t . p o l a r ( 5 , 0 . 9 2 7 2 9 5 )
19. 3/20/2014 Affordances http://localhost:9090/onepage 19/67 Example Find/Detect Smalltalk ­> Ruby
20. 3/20/2014 Affordances http://localhost:9090/onepage 20/67 # ( 2 4 6 8 ) d e t e c t : [ : e a c h | e a c h o d d ] " U n h a n d l e d e x c e p t i o n : E l e m e n t N o t F o u n d "
21. 3/20/2014 Affordances http://localhost:9090/onepage 21/67 [ 2 , 4 , 6 , 8 ] . f i n d { | n | n . o d d ? } # = > n i l
22. 3/20/2014 Affordances http://localhost:9090/onepage 22/67 # ( 2 4 6 8 ) d e t e c t : [ : e a c h | e a c h o d d ] i f N o n e : [ # n o n e ] " # n o n e "
23. 3/20/2014 Affordances http://localhost:9090/onepage 23/67 Affordance Multiple Blocks
24. 3/20/2014 Affordances http://localhost:9090/onepage 24/67 [ 2 , 4 , 6 , 8 ] . f i n d ( - > { : n o n e } ) { | n | n . o d d ? } # = > : n o n e
25. 3/20/2014 Affordances http://localhost:9090/onepage 25/67 Linguistic Relativity a.k.a. The Sapir­Whorf Hypothesis "[T]he structure of a language affects the ways in which its respective speakers conceptualize their world ... or otherwise influences their cognitive processes." ­­ http://en.wikipedia.org/wiki/Linguistic_relativity
26. 3/20/2014 Affordances http://localhost:9090/onepage 26/67 When Code Cries Cory Foy at SCNA 2012 http://vimeo.com/53986875 What does a language allow you to say? What does a language force you to say?
27. 3/20/2014 Affordances http://localhost:9090/onepage 27/67 The Power and Philsophy of Ruby Matz at OSCON 2003 http://www.rubyist.net/~matz/slides/oscon2003/mgp00001.html "Languages are not only tools to communicate, but also tools to think."
28. 3/20/2014 Affordances http://localhost:9090/onepage 28/67 Example Cleaning Up After Yourself C++ ­> Ruby
29. 3/20/2014 Affordances http://localhost:9090/onepage 29/67 i f ( ( e r r = S S L F r e e B u f f e r ( & h a s h C t x ) ) ! = 0 ) g o t o f a i l ; i f ( ( e r r = R e a d y H a s h ( & S S L H a s h S H A 1 , & h a s h C t x ) ) ! = 0 ) g o t o f a i l ; i f ( ( e r r = S S L H a s h S H A 1 . u p d a t e ( & h a s h C t x , & c l i e n t R a n d o m ) ) ! = g o t o f a i l ; i f ( ( e r r = S S L H a s h S H A 1 . u p d a t e ( & h a s h C t x , & s e r v e r R a n d o m ) ) ! = g o t o f a i l ; i f ( ( e r r = S S L H a s h S H A 1 . u p d a t e ( & h a s h C t x , & s i g n e d P a r a m s ) ) ! = g o t o f a i l ; g o t o f a i l ; i f ( ( e r r = S S L H a s h S H A 1 . f i n a l ( & h a s h C t x , & h a s h O u t ) ) ! = 0 ) g o t o f a i l ; / / . . . f a i l : S S L F r e e B u f f e r ( & s i g n e d H a s h e s ) ; S S L F r e e B u f f e r ( & h a s h C t x ) ; r e t u r n e r r ;
30. 3/20/2014 Affordances http://localhost:9090/onepage 30/67 # i n c l u d e " s u p p o r t . h " # i n c l u d e < i o s t r e a m > v o i d f o o ( ) { R e s o u r c e * r e s o u r c e = a c q u i r e R e s o u r c e ( ) ; b a r ( r e s o u r c e ) ; i f ( b a z ( r e s o u r c e ) ! = 4 2 ) r e t u r n ; s t d : : c o u t < < " C o m p l e t e d s u c c e s s f u l l y ! " < < s t d : : e n d l ; r e l e a s e R e s o u r c e ( r e s o u r c e ) ; }
31. 3/20/2014 Affordances http://localhost:9090/onepage 31/67 $ . / b r o k e n A c q u i r i n g r e s o u r c e C a u g h t e x c e p t i o n : o o p s !
32. 3/20/2014 Affordances http://localhost:9090/onepage 32/67 # i n c l u d e " s u p p o r t . h " # i n c l u d e < i o s t r e a m > v o i d f o o ( ) { R e s o u r c e * r e s o u r c e = a c q u i r e R e s o u r c e ( ) ; t r y { b a r ( r e s o u r c e ) ; i f ( b a z ( r e s o u r c e ) = = 4 2 ) { s t d : : c o u t < < " C o m p l e t e d s u c c e s s f u l l y ! " < < s t d : : e n d l ; } } c a t c h ( s t d : : e x c e p t i o n & e ) { r e l e a s e R e s o u r c e ( r e s o u r c e ) ; t h r o w ; } r e l e a s e R e s o u r c e ( r e s o u r c e ) ; }
33. 3/20/2014 Affordances http://localhost:9090/onepage 33/67 $ . / w o r d y A c q u i r i n g r e s o u r c e R e l e a s i n g r e s o u r c e C a u g h t e x c e p t i o n : o o p s !
34. 3/20/2014 Affordances http://localhost:9090/onepage 34/67 # i n c l u d e " s u p p o r t . h " # i n c l u d e < i o s t r e a m > v o i d f o o ( ) { R e s o u r c e * r e s o u r c e = a c q u i r e R e s o u r c e ( ) ; t r y { b a r ( r e s o u r c e ) ; i f ( b a z ( r e s o u r c e ) = = 4 2 ) { s t d : : c o u t < < " C o m p l e t e d s u c c e s s f u l l y ! " < < s t d : : e n d l ; } } c a t c h ( s t d : : e x c e p t i o n & e ) { r e l e a s e R e s o u r c e ( r e s o u r c e ) ; t h r o w ; } r e l e a s e R e s o u r c e ( r e s o u r c e ) ; }
35. 3/20/2014 Affordances http://localhost:9090/onepage 35/67
36. 3/20/2014 Affordances http://localhost:9090/onepage 36/67 RAII Resource Acquisition Is Initialization Acquire resources in the constructor Release them in the destructor
37. 3/20/2014 Affordances http://localhost:9090/onepage 37/67 # i n c l u d e " S a f e R e s o u r c e . h " # i n c l u d e " s u p p o r t . h " S a f e R e s o u r c e : : S a f e R e s o u r c e ( ) : r e s o u r c e ( a c q u i r e R e s o u r c e ( ) ) { } S a f e R e s o u r c e : : ~ S a f e R e s o u r c e ( ) { r e l e a s e R e s o u r c e ( r e s o u r c e ) ; } R e s o u r c e * S a f e R e s o u r c e : : g e t ( ) { r e t u r n r e s o u r c e ; }
38. 3/20/2014 Affordances http://localhost:9090/onepage 38/67 # i n c l u d e " S a f e R e s o u r c e . h " # i n c l u d e " s u p p o r t . h " # i n c l u d e < i o s t r e a m > v o i d f o o ( ) { S a f e R e s o u r c e r e s o u r c e ; b a r ( r e s o u r c e . g e t ( ) ) ; i f ( b a z ( r e s o u r c e . g e t ( ) ) ! = 4 2 ) r e t u r n s t d : : c o u t < < " C o m p l e t e d s u c c e s s f u l l y ! " < < s t d : : e n d l ; }
39. 3/20/2014 Affordances http://localhost:9090/onepage 39/67 $ . / r a i i A c q u i r i n g r e s o u r c e R e l e a s i n g r e s o u r c e C a u g h t e x c e p t i o n : o o p s !
40. 3/20/2014 Affordances http://localhost:9090/onepage 40/67 Affordance Deterministic Destructors
41. 3/20/2014 Affordances http://localhost:9090/onepage 41/67 Ruby doesn't have deterministic destructors. So what can we do instead?
42. 3/20/2014 Affordances http://localhost:9090/onepage 42/67 Blocks!
43. 3/20/2014 Affordances http://localhost:9090/onepage 43/67 c l a s s S a f e R e s o u r c e d e f s e l f . a c q u i r e r e s o u r c e = s e l f . n e w y i e l d r e s o u r c e e n s u r e r e s o u r c e . r e l e a s e e n d d e f i n i t i a l i z e p u t s " A c q u i r i n g r e s o u r c e " @ r e s o u r c e = O b j e c t . n e w e n d d e f r e l e a s e p u t s " R e l e a s i n g r e s o u r c e " @ r e s o u r c e = n i l e n d
44. 3/20/2014 Affordances http://localhost:9090/onepage 44/67 r e q u i r e _ r e l a t i v e " s u p p o r t " r e q u i r e _ r e l a t i v e " s a f e _ r e s o u r c e " d e f f o o S a f e R e s o u r c e . a c q u i r e d o | r e s o u r c e | b a r ( r e s o u r c e ) r e t u r n u n l e s s b a z ( r e s o u r c e ) = = 4 2 p u t s " C o m p l e t e d s u c c e s s f u l l y ! " e n d e n d
45. 3/20/2014 Affordances http://localhost:9090/onepage 45/67 $ r u b y d r i v e r . r b A c q u i r i n g r e s o u r c e R e l e a s i n g r e s o u r c e C a u g h t e x c e p t i o n : o o p s !
46. 3/20/2014 Affordances http://localhost:9090/onepage 46/67 Example ImageReader Smalltalk ­> Ruby
47. 3/20/2014 Affordances http://localhost:9090/onepage 47/67 I m a g e R e a d e r c l a s s > > f r o m F i l e : a F i l e n a m e | r e a d e r C l a s s i m a g e S t r e a m r e a d e r | i m a g e S t r e a m : = a F i l e n a m e r e a d S t r e a m b i n a r y . [ r e a d e r C l a s s : = s e l f r e a d e r C l a s s F o r : i m a g e S t r e a m . r e a d e r C l a s s i f N i l : [ ^ s e l f e r r o r : ' U n k n o w n i m a g e t y p e : ' , a F i l e n a m e a s S t r i n g ] . r e a d e r : = r e a d e r C l a s s o n : i m a g e S t r e a m ] e n s u r e : [ i m a g e S t r e a m c l o s e ] . ^ r e a d e r
48. 3/20/2014 Affordances http://localhost:9090/onepage 48/67 I m a g e R e a d e r c l a s s > > r e a d e r C l a s s F o r : i m a g e S t r e a m ^ s e l f s u b c l a s s e s d e t e c t : [ : e a c h C l a s s | i m a g e S t r e a m r e s e t . [ e a c h C l a s s c a n R e a d : i m a g e S t r e a m ] e n s u r e : [ i m a g e S t r e a m r e s e t ] ] i f N o n e : [ n i l ]
49. 3/20/2014 Affordances http://localhost:9090/onepage 49/67 Affordance Subclass Iteration
50. 3/20/2014 Affordances http://localhost:9090/onepage 50/67 c l a s s I m a g e R e a d e r d e f s e l f . r e a d ( f i l e n a m e ) F i l e . o p e n ( f i l e n a m e , " r b " ) d o | i o | r e a d e r _ c l a s s = f i n d _ r e a d e r _ c l a s s ( i o ) r a i s e " U n k n o w n i m a g e t y p e : # { f i l e n a m e } " u n l e s s r e a d e r _ c l a s s r e a d e r _ c l a s s . n e w ( i o ) e n d e n d # . . . e n d
51. 3/20/2014 Affordances http://localhost:9090/onepage 51/67 c l a s s I m a g e R e a d e r # . . . d e f s e l f . f i n d _ r e a d e r _ c l a s s ( i o ) s u b c l a s s e s . f i n d { | r e a d e r | b e g i n i o . r e w i n d r e a d e r . c a n _ r e a d ? ( i o ) e n s u r e i o . r e w i n d e n d } e n d # . . . e n d
52. 3/20/2014 Affordances http://localhost:9090/onepage 52/67 c l a s s I m a g e R e a d e r # . . . d e f s e l f . i n h e r i t e d ( s u b c l a s s ) s u b c l a s s e s < < s u b c l a s s e n d d e f s e l f . s u b c l a s s e s @ s u b c l a s s e s | | = [ ] e n d # . . . e n d
53. 3/20/2014 Affordances http://localhost:9090/onepage 53/67 c l a s s B M P I m a g e R e a d e r < I m a g e R e a d e r d e f s e l f . c a n _ r e a d ? ( i o ) i o . r e a d ( 2 ) = = " B M " e n d d e f r e a d _ i m a g e p u t s " R e a d i n g B M P " e n d e n d
54. 3/20/2014 Affordances http://localhost:9090/onepage 54/67 c l a s s J P G I m a g e R e a d e r < I m a g e R e a d e r d e f s e l f . c a n _ r e a d ? ( i o ) i o . r e a d ( 2 ) = = " \ x F F \ x D 8 " . b e n d d e f r e a d _ i m a g e p u t s " R e a d i n g J P G " e n d e n d
55. 3/20/2014 Affordances http://localhost:9090/onepage 55/67 c l a s s P N G I m a g e R e a d e r < I m a g e R e a d e r d e f s e l f . c a n _ r e a d ? ( i o ) i o . r e a d ( 8 ) = = " \ x 8 9 P N G \ r \ n \ x 1 A \ n " . b e n d d e f r e a d _ i m a g e p u t s " R e a d i n g P N G " e n d e n d
56. 3/20/2014 Affordances http://localhost:9090/onepage 56/67 r e q u i r e _ r e l a t i v e " i m a g e _ r e a d e r s " % w { b m p j p g p n g } . e a c h d o | e x t | I m a g e R e a d e r . r e a d ( " e x a m p l e . # { e x t } " ) e n d
57. 3/20/2014 Affordances http://localhost:9090/onepage 57/67 $ r u b y s u b c l a s s e s . r b R e a d i n g B M P R e a d i n g J P G R e a d i n g P N G
58. 3/20/2014 Affordances http://localhost:9090/onepage 58/67 Takeaways
59. 3/20/2014 Affordances http://localhost:9090/onepage 59/67 Languages afford certain designs and inhibit others
60. 3/20/2014 Affordances http://localhost:9090/onepage 60/67 Languages influence thought
61. 3/20/2014 Affordances http://localhost:9090/onepage 61/67 Learning new languages will increase your "solution space"
62. 3/20/2014 Affordances http://localhost:9090/onepage 62/67 Don't go too far
63. 3/20/2014 Affordances http://localhost:9090/onepage 63/67 Want More? http://randycoulman.com/blog/categories/affordances/
64. 3/20/2014 Affordances http://localhost:9090/onepage 64/67 Acknowledgements Key Technology (http://www.key.net/) Rogue.rb (@roguerb) Jen Myers (@antiheroine)
65. 3/20/2014 Affordances http://localhost:9090/onepage 65/67 References The Design of Every Day Things ­ Donald Norman Coding Out Loud ­ Amir Rajan Linguistic Relativity ­ Wikipedia article When Code Cries ­ Cory Foy at SCNA 2012 The Power and Philosophy of Ruby ­ Matz at OSCON 2003
66. 3/20/2014 Affordances http://localhost:9090/onepage 66/67 Questions?
67. 3/20/2014 Affordances http://localhost:9090/onepage 67/67 Randy Coulman http://speakerrate.com/randycoulman http://www.slideshare.net/randycoulman http://randycoulman.com @randycoulman randycoulman