Programming with Birds - There is a Bluebird in My Talk That Wants to Get Out (LambdAle 2018)

These are the slides for my talk at LambdAle 2018 in London, UK.

The whole idea here is to show people how Lambda Calculus works, how to encode data using functions and demonstrate its Turing-Completeness. I then proceed to explain combinators and replace the functions with combinators and then replace the combinators themselves with only S and K, the smallest combinator base possible for completeness.

This talk is inspired in the excellent "Programming With Nothing" by Tom Stuart, the main difference is that in this one I use JavaScript and I also added combinators and SK calculus. My take is a bit different, but Tom's talk is definitely worth watching (one of the best I've ever seen).

Transcript

1. 100 1 There is a Bluebird in my Talk that Wants to Get out Programming with birds THEWIZARDLUCAS
2. 100 2 PROGRAMMING IS A GREAT EXPERIENCE
3. 100 3 I want to make it awful. And I'm not the first one. Programming with nothing By Tom Stuart
4. 100 4 I want to make it awful. But I want to take it one step further. z Programming with nothing By Tom Stuart
5. 100 5 Ruin JavaScript Part 1
6. 100 6 Ruin JavaScript Ruin JavaScript with birds Part 1 Part 2
7. 100 7 Ruin JavaScript Ruin JavaScript with birds Ruin JavaScript and The Birds Part 1 Part 2 Part 3
8. 100 8 Ruin JavaScript Ruin JavaScript with birds Ruin JavaScript and The Birds Part 1 Part 2 Part 3 Apologise Part 4
9. 100 9 Ruining JavaScript Part 1
10. 100 10 We are spoiled We program with way too much: • Objects • Classes/Inheritance • Booleans • Numbers • Builtin functions • Builtin data structures
11. 100 11 This is what we're going to rewrite T H E W R E C K
12. 100 12 We are only allowed to use four kinds of tokens THE RULES 1 2 3 4 Identifier ID λID. E E E (E) Abstraction Application Grouping
13. 100 13 We are only allowed to use four kinds of tokens THE RULES 1 2 3 4 Identifier ID λID. E E E (E) Abstraction Application Grouping Yes, all functions only take one argument I will use assignments to make this more convenient In JavaScript this is E(E)
14. 100 14 Lambda Calculus This is λ
15. 100 15 Our first step T H E W R E C K
16. 100 16 Replacing Booleans P a r t 1
17. 100 17 Why do we need booleans anyway? Replacing Numbers if { this } else { that } const val = boolean ? "Yes": "No"
18. 100 18 Why do we need booleans anyway? Replacing Numbers if { this } else { that } const val = boolean ? "Yes": "No" const TRUE = a => b => a Always selects the first value.
19. 100 19 Why do we need booleans anyway? Replacing Numbers if { this } else { that } const val = boolean ? "Yes": "No" const FALSE = a => b => b Always selects the second value.
20. 100 20 Booleans Replacing Numbers const FALSE = a => b => b const TRUE = a => b => a
21. 100 21 Booleans Replacing Numbers const SECOND = a => b => b const FIRST = a => b => a
22. 100 22 Booleans Replacing Numbers
23. 100 23 Booleans Replacing Numbers What about the if keyword?
24. 100 24 Booleans Replacing Numbers What about the if keyword? if { this } else { that }
25. 100 25 Booleans Replacing Numbers What about the if keyword? BOOLEAN { this } else { that }
26. 100 26 Booleans Replacing Numbers What about the if keyword? BOOLEAN { this } { that }
27. 100 27 Booleans Replacing Numbers What about the if keyword? BOOLEAN { this } { that } The boolean itself is our this.
28. 100 28 Booleans Replacing Numbers Let's have some sugar
29. 100 29 What can we replace? Replacing arithmetics
30. 100 30 Replacing Numbers P a r t 1
31. 100 31 What is a number, anyway? Replacing Numbers 2
32. 100 32 What is a number, anyway? Replacing Numbers 2
33. 100 33 What is a number, anyway? Replacing Numbers 2
34. 100 34 What is a number, anyway? Replacing Numbers 2 Representation Meaning Meaning
35. 100 35 How can we represent quantities with functions? Replacing Numbers
36. 100 36 How can we represent quantities with functions? Replacing Numbers Function applications!
37. 100 37 How can we represent quantities with functions? Replacing Numbers Function applications!
38. 100 38 How can we represent quantities with functions? Replacing Numbers Function applications!
39. 100 39 How can we represent quantities with functions? Replacing Numbers Function applications!
40. 100 40 From meaning to representation Replacing Numbers
41. 100 41 From meaning to representation Replacing Numbers
42. 100 42 From meaning to representation Replacing Numbers
43. 100 43 From meaning to representation Replacing Numbers
44. 100 44 From meaning to representation Replacing Numbers
45. 100 45 What can we replace? Replacing arithmetics
46. 100 46 Replacing Arithmetics P a r t 1
47. 100 47 The successor function Replacing arithmetics const ONE = f => x => f(x) const TWO = f => x => f(f(x))
48. 100 48 The successor function Replacing arithmetics const ONE = f => x => f(x) const SUCCESSOR = n => f => x => f(n(f)(x)) const TWO = f => x => f(f(x))
49. 100 49 The successor function Replacing arithmetics const ONE = f => x => f(x) SUCCESSOR(ONE) const TWO = f => x => f(f(x)) const SUCCESSOR = n => f => x => f(n(f)(x))
50. 100 50 The successor function Replacing arithmetics const ONE = f => x => f(x) SUCCESSOR(ONE) f => x => f((ONE(f))(x)) const TWO = f => x => f(f(x)) const SUCCESSOR = n => f => x => f(n(f)(x))
51. 100 51 The successor function Replacing arithmetics const ONE = f => x => f(x) SUCCESSOR(ONE) f => x => f((ONE(f))(x)) f => x => f((x => f(x))(x)) const TWO = f => x => f(f(x)) const SUCCESSOR = n => f => x => f(n(f)(x))
52. 100 52 The successor function Replacing arithmetics const ONE = f => x => f(x) f => x => f((ONE(f))(x)) f => x => f((x => f(x))(x)) f => x => f(f(x)) const TWO = f => x => f(f(x)) const SUCCESSOR = n => f => x => f(n(f)(x)) SUCCESSOR(ONE)
53. 100 53 The addition function Replacing arithmetics const TWO = f => x => f(f(x)) const ONE = f => x => f(x)
54. 100 54 The addition function Replacing arithmetics const TWICE = f => x => f(f(x)) const ONE = f => x => f(x)
55. 100 55 The addition function Replacing arithmetics twice(SUCCESSOR(ONE)) ADDITION(TWO)(ONE)
56. 100 56 The multiplication function Replacing arithmetics
57. 100 57 The multiplication function Replacing arithmetics multiplication(THREE)(TWO)
58. 100 58 The multiplication function Replacing arithmetics THRICE(TWO) multiplication(THREE)(TWO)
59. 100 59 What can we replace? Replacing arithmetics
60. 100 60 What can we replace? Replacing arithmetics
61. 100 61 What is next? Replacing arithmetics Subtraction
62. 100 62 The predecessor function Replacing arithmetics Predecessor TWO ONE
63. 100 63 The predecessor function Replacing arithmetics TWO ONE ?
64. 100 64 Pairs Replacing arithmetics
65. 100 65 Pairs Replacing arithmetics First we store two values.
66. 100 66 Pairs Replacing arithmetics Then we tell which one we want.
67. 100 67 Pairs Replacing arithmetics
68. 100 68 Pairs Replacing arithmetics
69. 100 69 Pairs Replacing arithmetics
70. 100 70 Pairs Replacing arithmetics
71. 100 71 Pairs Replacing arithmetics
72. 100 72 Replacing arithmetics Incrementing Pairs { 0, 1 } { 0, 0 }
73. 100 73 Replacing arithmetics { 1, 2 } Incrementing Pairs { 0, 1 } { 0, 0 }
74. 100 74 Replacing arithmetics { 1, 2 } { 2, 3 } Incrementing Pairs { 0, 1 } { 0, 0 }
75. 100 75 Replacing arithmetics { 1, 2 } { 2, 3 } { 4, 5 } Incrementing Pairs { 0, 1 } { 0, 0 }
76. 100 76 Replacing arithmetics { 1, 2 } { 2, 3 } { 4, 5 } { 5, 6 } Incrementing Pairs { 0, 1 } { 0, 0 }
77. 100 77 Replacing arithmetics { 1, 2 } { 2, 3 } { 4, 5 } { 5, 6 } { 0, 0 } Thrice Incrementing Pairs { 0, 1 } { 0, 0 }
78. 100 78 Replacing arithmetics { 1, 2 } { 2, 3 } { 4, 5 } { 5, 6 } { 0, 0 } Thrice { 0, 1 } Incrementing Pairs { 0, 1 } { 0, 0 } x1
79. 100 79 Replacing arithmetics { 1, 2 } { 2, 3 } { 4, 5 } { 5, 6 } { 0, 0 } Thrice { 1, 2 } Incrementing Pairs { 0, 1 } { 0, 0 } x2
80. 100 80 Replacing arithmetics { 1, 2 } { 2, 3 } { 4, 5 } { 5, 6 } { 0, 0 } Thrice { 2, 3 } Incrementing Pairs { 0, 1 } { 0, 0 } x3
81. 100 81 Replacing arithmetics { 1, 2 } { 2, 3 } { 4, 5 } { 5, 6 } { 0, 0 } Thrice { 2, 3 } Incrementing Pairs { 0, 1 } { 0, 0 } x3
82. 100 82 Replacing arithmetics { 1, 2 } { 2, 3 } { 4, 5 } { 5, 6 } { 0, 0 } Three { 2, 3 } Incrementing Pairs { 0, 1 } { 0, 0 } x3 Predecessor
83. 100 83 Replacing arithmetics The Predecessor Function N x INCREMENT_PAIR(0, 0) First of
84. 100 84 Replacing arithmetics The Subtraction Function Predecessor of N K times
85. 100 85 What can we replace? Replacing arithmetics
86. 100 86 What can we replace? Replacing arithmetics
87. 100 87 Replacing Boolean Operators P a r t 1
88. 100 88 AND { true } { true } is true AND Replacing Boolean Operators Any other combinations are false
89. 100 89 AND { true } { true } is true AND Replacing Boolean Operators Any other combinations are false
90. 100 90 AND Replacing Boolean Operators If a is true b must be true If a is false it returns itself
91. 100 91 It is true if any values are { true } OR Replacing Boolean Operators
92. 100 92 It is true if any values are { true } OR Replacing Boolean Operators
93. 100 93 It is true if any values are { true } OR Replacing Boolean Operators If a is true it returns itself, otherwise tries b
94. 100 94 NOT Replacing Boolean Operators Inverts any { true } and { false }
95. 100 95 NOT Replacing Boolean Operators Inverts any { true } and { false }
96. 100 96 NOT Replacing Boolean Operators Inverts any { true } and { false }
97. 100 97 NOT Replacing Boolean Operators Inverts any { true } and { false } Takes a boolean f and applies it to the arguments in reverse order
98. 100 98 NOT Replacing Boolean Operators Inverts the selector Takes a boolean f and applies it to the arguments in reverse order
99. 100 99 NOT Replacing Boolean Operators Inverts the selector Takes a boolean f and applies it to the arguments in reverse order
100. 100 100 IS ZERO Replacing Boolean Operators Checks if a is zero If n is zero, it will return the last TRUE
101. 100 101 EQUALS Replacing Boolean Operators Checks if a equals b Checks if both n <= k and k <= n
102. 100 102 GREATER THAN Replacing Boolean Operators The opposite of lesser or equal
103. 100 103 What can we replace? Replacing Boolean Operators
104. 100 104 What can we replace? Replacing Boolean Operators
105. 100 105 Replacing everything with functions Ruining Javascript
106. 100 106 Ruining Javascript Replacing everything with functions
107. 100 107 Ruining Javascript Replacing everything with functions
108. 100 108 Ruining Javascript Replacing everything with functions
109. 100 109 Ruining Javascript Replacing everything with functions
110. 100 110 Ruining Javascript Replacing everything with functions
111. 100 111 Ruining Javascript We could replace the names of these functions by their definitions and remove all variable names Replacing everything with functions
112. 100 112 Unleash Hell Ruining Javascript But I will save you from this pain for now
113. 100 113 Ruining JavaScript With Birds Part 2
114. 100 114 Combinators Our Birds Functions that don't have free variables. const combinator = a => b => a const withContext = a => b(a) a is bound and b is free both a and b are bound
115. 100 115 To Mock a Mockingbird C o m b i n a t o r s a n d B i r d s
116. 100 116 Combinators The Idiot Bird
117. 100 117 Combinators The Kestrel
118. 100 118 Combinators The Kestrel
119. 100 119 Combinators The Cardinal
120. 100 120 Combinators The Vireo
121. 100 121 Combinators The Bluebird
122. 100 122 Combinators The Thrush
123. 100 123 Combinators The Starling
124. 100 124 Combinators Replacing Functions (Successor) const SUCCESSOR = n => f => x => f(n(f)(x))
125. 100 125 Combinators const SUCCESSOR = n => f => B(f)(n(f)) Replacing Functions (Successor)
126. 100 126 Combinators const SUCCESSOR = n => f => B(f)(n(f)) Replacing Functions (Successor)
127. 100 127 Combinators const SUCCESSOR = n => f => B(f)(n(f)) const SUCCESSOR = S(B) Replacing Functions (Successor)
128. 100 128 Combinators Replacing Functions (Addition) const ADDITION = n => k => n(SUCESSOR)(k)
129. 100 129 Combinators Replacing Functions (Addition) const ADDITION = n => k => n(S(B))(k)
130. 100 130 Combinators Replacing Functions (Addition) const ADDITION = k => Th(S(B))(k)
131. 100 131 Combinators Replacing Functions (Addition) const ADDITION = C(Th)(Th(S(B)))
132. 100 132 Nice birds m8 Ruining Javascript
133. 100 133 Ruining Javascript B Th C K KI V S Nice birds m8
134. 100 134 Ruining Javascript Haskell's Data.Aviary.Birds This module is intended for illustration (the type signatures!) rather than utility.
135. 100 135 Ruining Javascript Nice birds m8
136. 100 136 Ruining JavaScript and the Birds Part 3
137. 100 137 WHAT IF I TOLD YOU YOU ONLY NEED TWO COMBINATORS? Yes, that's right. Two.
138. SK SK Calculus S K
139. 100 139 SK Calculus Replacing Numbers People also call it SKI Calculus
140. 100 140 SK Calculus Replacing Numbers People also call it SKI Calculus Because it's more convenient to have I
141. 100 141 SK Calculus Replacing Numbers People also call it SKI Calculus const I = S(K)(K) Because it's more convenient to have I
142. 100 142 SK Calculus Replacing Numbers const KI = K(S(K)(K))
143. 100 143 SK Calculus Replacing Numbers const KI = K(I)
144. 100 144 SK Calculus Replacing Numbers const KI = K(I) const B = S(K(S))(K)
145. 100 145 SK Calculus Replacing Numbers const KI = K(I) const B = S(K(S))(K) const V = PAIRING
146. 100 146 SK Calculus Replacing Numbers const V = ((S(K((S((S(K((S(KS) )K)))S))(KK)))) ((S(K(S((SK)K))))K))
147. 100 147 SK Calculus Replacing Numbers const V = ((S(K((S((S(K((S(KS) )K)))S))(KK)))) ((S(K(S((SK)K))))K)) Easy.
148. 100 148 What does this mean?
149. 100 149 What does this mean? If we can replace all code by functions
150. 100 150 What does this mean? If we can replace all code by functions Replace all functions by combinators
151. 100 151 What does this mean? If we can replace all code by functions Replace all functions by combinators And replace all combinators by S and K
152. 100 152 What does this mean? If we can replace all code by functions Replace all functions by combinators And replace all combinators by S and K Then we can replace all code by S and K
153. 100 153 What does this mean? https://crypto.stanford.edu/~blynn/lambda/sk.html http://xn--wxak1a.com/blog/Combinators.html
154. 100 154 Apologising Part 4
155. 100 155 Apologising Part 4 Functional Programming Combinatory Logic Computability Theory History of Math Compiler Theory Language Design Recursion Wanting to frame
 Gödel pictures to hang in your room
156. 100 156 Thank you! Shhh, no tears. Only lambdas now. @THEWIZARDLUCAS (TWITTER) @LUCASFCOSTA (GITHUB) LUCASFCOSTA.COM
157. 100 157 References http://codon.com/programming-with-nothing http://www.angelfire.com/tx4/cus/combinator/birds.html https://bit.ly/2xpcPKn A Flock of Functions - Gabriel Lebec List of Notorious Combinators The blog post for the talk I mentioned in the beginning https://speakerdeck.com/tomstuart/programming-with-nothing Slides for the talk "Programming with Nothing" https://amzn.to/2BVVsa1 To Mock a Mockingbird - Raymond Smullyan http://computationbook.com Understanding Computation - Tom Stuart https://www.youtube.com/watch?v=_kYGDJSm0gE - ASU Lectures - Lambda Calculus by Adam Doupé
158. 100 158 Thank you! Shhh, no tears. Only lambdas now. @THEWIZARDLUCAS (TWITTER) @LUCASFCOSTA (GITHUB) LUCASFCOSTA.COM