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
   

   View Slide

2. View Slide

3. $$$
   

   View Slide

4. 
   

   View Slide

5. $$$
   

   View Slide

6. def total_price
   200 + volume * distance
   end
   

   View Slide

7. def total_price
   200 + volume * distance
   end
   sum
   

   View Slide

8. def total_price
   200 + volume * distance
   end
   sum
   product
   

   View Slide

9. def total_price
   200 + volume * distance
   end
   sum
   product
   variable
   

   View Slide

10. def total_price
    200 + volume * distance
    end
    sum
    product
    constant
    variable
    

    View Slide

11. View Slide

12. class Sum
    def initialize(left, right)
    @left = left
    @right = right
    end
    end
    

    View Slide

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
    

    View Slide

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
    

    View Slide

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
    

    View Slide

16. def price_formula
    Sum.new(
    Constant.new(200),
    Product.new(
    Variable.new(Fvolume),
    Variable.new(Fdistance),
    )
    )
    end
    

    View Slide

17. input = {
    volume: 20,
    distance: 200,
    }
    price_formula.evaluate(input)
    

    View Slide

18. class Variable
    def initialize(name)
    @name = name
    end
    def evaluate(input)
    input.fetch(@name)
    end
    end
    

    View Slide

19. class Constant
    def initialize(value)
    @value = value
    end
    def evaluate(_input)
    @value
    end
    end
    

    View Slide

20. class Sum
    def initialize(left, right)
    @left = left
    @right = right
    end
    def evaluate(input)
    @left.evaluate(input) + @right.evaluate(input)
    end
    end
    

    View Slide

21. class Product
    def initialize(left, right)
    @left = left
    @right = right
    end
    def evaluate(input)
    @left.evaluate(input) * @right.evaluate(input)
    end
    end
    

    View Slide

22. def price_formula
    Sum.new(
    Constant.new(200),
    Product.new(
    Variable.new(Fvolume),
    Variable.new(Fdistance),
    ),
    )
    end
    

    

    

    

    View Slide

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
    

    View Slide

24. class AbstractExpr
    def +(other)
    Sum.new(self, other)
    end
    def *(other)
    Product.new(self, other)
    end
    end
    

    View Slide

25. class Sum < AbstractExpr
    # …
    end
    class Product < AbstractExpr
    # …
    end
    class Constant < AbstractExpr
    # …
    end
    class Variable < AbstractExpr
    # …
    end
    

    View Slide

26. def price_formula
    Constant.new(200) + Variable.new(Fvolume) * Variable.new(Fdistance)
    end
    

    View Slide

27. THE POINT
    

    View Slide

28. Constant.new(200) + Variable.new(Fvolume) * Variable.new(Fdistance)

    

    

    

    

    

    

    

    

    View Slide

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
    

    View Slide

30. class Node
    def initialize(name, value, children)
    @name = name
    @value = value
    @children = children
    end
    end
    

    View Slide

31. + UV> 4200
    const UV> 200
    * UV> 4000
    var volume UV> 20
    var distance UV> 200
    

    View Slide

32. + UV> 4200
    const UV> 200
    * UV> 4000
    var volume UV> 20
    var distance UV> 200
    Node.new("+", 4200, [const_node, product_node])
    

    View Slide

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, [])
    

    View Slide

34. class Variable < AbstractExpr
    def initialize(name)
    @name = name
    end
    def evaluate(input)
    Node.new(
    "var #{@name}",
    input.fetch(@name),
    [],
    )
    end
    end
    

    View Slide

35. class Constant
    def initialize(value)
    @value = value
    end
    def evaluate(_input)
    Node.new(
    'const',
    @value,
    [],
    )
    end
    end
    

    View Slide

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
    

    View Slide

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
    

    View Slide

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
    

    View Slide

39. puts price_formula.evaluate(input)

    

    

    

    

    

    

    View Slide

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

    View Slide

41. puts price_formula.evaluate(input).value

    

    

    View Slide

42. puts price_formula.evaluate(input).value

    

    4200
    

    View Slide

43. + UV> 4200
    const UV> 200
    * UV> 4000
    var volume UV> 20
    var distance UV> 200
    

    View Slide

44. +
    (= 4200)
    const
    (= 200)
    *
    (= 4000)
    var distance
    (= 200)
    var volume
    (= 20)
    

    View Slide

45. IDEA: translate to SQL
    

    View Slide

46. IDEA: compile with LLVM
    

    View Slide

47. What about input?
    

    View Slide

48. BACKEND
    

    View Slide

49. BACKEND formula
    

    View Slide

50. BACKEND
    PARSE +
    SERIALIZE
    formula
    

    View Slide

51. PARSING:

    parse("200 + volume * distance")
    

    

    

    

    

    

    

    

    

    

    

    View Slide

52. PARSING:

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

    

    

    

    

    View Slide

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

    

    View Slide

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"]]
    

    View Slide

55. BACKEND
    PARSE +
    SERIALIZE
    formula
    

    View Slide

56. BACKEND
    PARSE +
    SERIALIZE
    DESERIALIZE
    + UNPARSE
    formula
    

    View Slide

57. formula
    

    View Slide

58. formula A (stable)
    formula B (testing)
    

    View Slide

59. formula A (old)
    formula B (stable)
    

    View Slide

60. Is this over-engineering?
    

    View Slide

61. TAKE-AWAYS
    

    View Slide

62. * It’s much easier to reason about data

    than to reason about code.
    

    

    

    View Slide

63. * It’s much easier to reason about data

    than to reason about code.
    * Try novel approaches; they can

    reveal new opportunities.
    

    View Slide

64. View Slide