Code as data

Given at RUG::B’s July 2018 edition (http://www.rug-b.de/topics/code-as-data-606).

Transcript

1. CODE AS DATA DENIS DEFREYNE / RUG-.B / 2018-07-05
3. $$$
4. <disclaimer>
5. $$$
6. def total_price 200 + volume * distance end
7. def total_price 200 + volume * distance end sum
8. def total_price 200 + volume * distance end sum product
9. def total_price 200 + volume * distance end sum product variable
10. def total_price 200 + volume * distance end sum product constant variable
12. class Sum def initialize(left, right) @left = left @right = right end end
13. class Sum def initialize(left, right) @left = left @right = right end end class Product def initialize(left, right) @left = left @right = right end end
14. class Sum def initialize(left, right) @left = left @right = right end end class Product def initialize(left, right) @left = left @right = right end end class Constant def initialize(value) @value = value end end
15. class Sum def initialize(left, right) @left = left @right = right end end class Product def initialize(left, right) @left = left @right = right end end class Constant def initialize(value) @value = value end end class Variable def initialize(name) @name = name end end
16. def price_formula Sum.new( Constant.new(200), Product.new( Variable.new(Fvolume), Variable.new(Fdistance), ) ) end
17. input = { volume: 20, distance: 200, } price_formula.evaluate(input)
18. class Variable def initialize(name) @name = name end def evaluate(input) input.fetch(@name) end end
19. class Constant def initialize(value) @value = value end def evaluate(_input) @value end end
20. class Sum def initialize(left, right) @left = left @right = right end def evaluate(input) @left.evaluate(input) + @right.evaluate(input) end end
21. class Product def initialize(left, right) @left = left @right = right end def evaluate(input) @left.evaluate(input) * @right.evaluate(input) end end
22. def price_formula Sum.new( Constant.new(200), Product.new( Variable.new(Fvolume), Variable.new(Fdistance), ), ) end 
 
 

23. def price_formula Sum.new( Constant.new(200), Product.new( Variable.new(Fvolume), Variable.new(Fdistance), ) ) end def price_formula Constant.new(200) + Variable.new(Fvolume) * Variable.new(Fdistance) end
24. class AbstractExpr def +(other) Sum.new(self, other) end def *(other) Product.new(self, other) end end
25. class Sum < AbstractExpr # … end class Product < AbstractExpr # … end class Constant < AbstractExpr # … end class Variable < AbstractExpr # … end
26. def price_formula Constant.new(200) + Variable.new(Fvolume) * Variable.new(Fdistance) end
27. THE POINT
28. Constant.new(200) + Variable.new(Fvolume) * Variable.new(Fdistance)
 
 
 
 
 
 
 

29. Constant.new(200) + Variable.new(Fvolume) * Variable.new(Fdistance)
 
 
 
 + UV> 4200 const UV> 200 * UV> 4000 var volume UV> 20 var distance UV> 200
30. class Node def initialize(name, value, children) @name = name @value = value @children = children end end
31. + UV> 4200 const UV> 200 * UV> 4000 var volume UV> 20 var distance UV> 200
32. + UV> 4200 const UV> 200 * UV> 4000 var volume UV> 20 var distance UV> 200 Node.new("+", 4200, [const_node, product_node])
33. + UV> 4200 const UV> 200 * UV> 4000 var volume UV> 20 var distance UV> 200 Node.new("+", 4200, [const_node, product_node]) Node.new("var volume", 20, [])
34. class Variable < AbstractExpr def initialize(name) @name = name end def evaluate(input) Node.new( "var #{@name}", input.fetch(@name), [], ) end end
35. class Constant def initialize(value) @value = value end def evaluate(_input) Node.new( 'const', @value, [], ) end end
36. class Sum def initialize(left, right) @left = left @right = right end def evaluate(input) left_node = @left.evaluate(input) right_node = @right.evaluate(input) Node.new( '+', left_node.value + right_node.value, [left_node, right_node], ) end end
37. class Product def initialize(left, right) @left = left @right = right end def evaluate(input) left_node = @left.evaluate(input) right_node = @right.evaluate(input) Node.new( '*', left_node.value * right_node.value, [left_node, right_node], ) end end
38. class Node def to_s "#{@name} UV> #{@value}\n" + @children.map { |c| indent(c.to_s) }.join('') end private def indent(s) s.lines.map { |l| ' ' + l }.join('') end end
39. puts price_formula.evaluate(input)
 
 
 
 
 

40. puts price_formula.evaluate(input) + ./> 4200 const ./> 200 * ./> 4000 var volume ./> 20 var distance ./> 200
41. puts price_formula.evaluate(input).value
 

42. puts price_formula.evaluate(input).value
 
 4200
43. + UV> 4200 const UV> 200 * UV> 4000 var volume UV> 20 var distance UV> 200
44. + (= 4200) const (= 200) * (= 4000) var distance (= 200) var volume (= 20)
45. IDEA: translate to SQL
46. IDEA: compile with LLVM
47. What about input?
48. BACKEND
49. BACKEND formula
50. BACKEND PARSE + SERIALIZE formula
51. PARSING:
 parse("200 + volume * distance") 
 
 
 
 
 
 
 
 
 

52. PARSING:
 parse("200 + volume * distance") D> Sum.new( Constant.new(200), Product.new( Variable.new(Kvolume), Variable.new(Kdistance), ) )
 
 
 

53. SERIALIZING: formula = Sum.new( Constant.new(200), Product.new( Variable.new(Fvolume), Variable.new(Fdistance), ) ) serialize(formula) 

54. SERIALIZING: formula = Sum.new( Constant.new(200), Product.new( Variable.new(Fvolume), Variable.new(Fdistance), ) ) serialize(formula) D> ["sum", ["constant", 200], ["product", ["var", "volume"], ["var", "distance"]]
55. BACKEND PARSE + SERIALIZE formula
56. BACKEND PARSE + SERIALIZE DESERIALIZE + UNPARSE formula
57. formula
58. formula A (stable) formula B (testing)
59. formula A (old) formula B (stable)
60. Is this over-engineering?
61. TAKE-AWAYS
62. * It’s much easier to reason about data
 than to reason about code. 
 

63. * It’s much easier to reason about data
 than to reason about code. * Try novel approaches; they can
 reveal new opportunities.