This is an implementation of a relational logic programming system, μKanren, a minimalist version of miniKanren. I’m not an expert on any of these things, just interested in hacking on fun tools and learning about new things. I’ve found Hy to be a unique opportunity to explore Python internals and data science libraries, while also playing to the strengths of Python. Code: https://github.com/mudphone/Hywaii

1. Relational
Programming
Kyle Oba
koba@pasdechocolat.com
@mudphone
Freelance Professor
μKanren in Hy

2. PYTHON!

3. miniKanren

4. μKanren

5. μKanren
miniKanren
The Reasoned Schemer
Hywai‘i
+ 36 sloc user forms
+ 197 sloc user forms

6. github.com/mudphone/Hywaii

7. –Hy docs
http://hy.readthedocs.org/en/latest/tutorial.html
“Hy is lisp-stick on a Python!”

8. Python
Hy
μKanren
The Idea: miniKanren

9. Python Hy μKanren

10. WTF
Hy Lisp?

11. –John Foderaro, CACM
http://www.paulgraham.com/chameleon.html
“Lisp is a programmable programming language.”

12. LISP

13. Relational?

14. SQL is DECLARATIVE

15. SELECT User.name
FROM User, Address
WHERE User.ID = Address.UserID
AND Address.State = ‘HI’;

16. It’s near the old
Costco.

18. How do relational
databases even work?

19. Tables Relationships
Query
Results
Facts
Questions
Answers
RELATIONAL DATABASE

20. SELECT User.name
FROM User, Address
WHERE User.ID = Address.UserID
AND Address.State = ‘HI’;
Name StateUserIDID
User Address
x x ‘HI’q
SQL QUERY

21. [[sally :age 21]
[fred :age 42]
[ethel :age 42]
[fred :likes pizza]
[sally :likes opera]
[ethel :likes sushi]]
[:find ?e
:where [?e :age 42]]
Facts
Questions
Answers [[fred], [ethel]]
DATALOG

22. [:find ?e
:where [?e :age 42]]
Name StateUserIDID
User Address
x x ‘HI’q
DATALOG
SQL QUERY

23. (run*
(fresh [q]
(appendo [1 2] [3 4] q)))
;; => [[1 2 3 4]]
(run*
(fresh [q]
(appendo [1 2] q [1 2 3 4])))
;; => [[3 4]]
μKanren

24. Relational
(Logic)
Programming

25. The HELLO WORLD
of logic programming
APPENDO

26. (run*
(fresh [q]
(== q 5)))
;; => [5]

27. (run*
(fresh [q]
(== 1 1)))
;; => ['_.0']

28. (run*
(fresh [q]
(== 1 2)))
;; => []

29. (run*
(fresh [x y]
(== y 6)
(== x y)))
;; => [6]

30. (run*
(fresh [q]
(conde [(== q 5)]
[(== q 6)])))
;; => [5, 6]

31. (run*
(fresh [x y]
(conde [(== y 5) (== x y)]
[(== x 6)])))
;; => [5, 6]

32. (defn caro [p a]
(fresh [d]
(== (cons a d) p)))
(defn cdro [p d]
(fresh [a]
(== (cons a d) p)))
(defn conso [a d p]
(== (cons a d) p))
(defn nullo [x]
(== [] x))

33. (run*
(fresh [q]
(appendo [1 2] [3 4] q)))
;; => [[1 2 3 4]]
(run*
(fresh [q]
(appendo [1 2] q [1 2 3 4])))
;; => [[3 4]]

34. (run*
(fresh [q x y]
(appendo x y [1 2 3 4])))
;; => ['_.0', '_.0', '_.0', '_.0', '_.0']
(run*
(fresh [q x y]
(appendo x y [1 2 3 4])
(== [x y] q)))
;; => [[[], [1 2 3 4]],
;; [[1], [2 3 4]],
;; [[1 2], [3 4]],
;; [[1 2 3], [4]],
;; [[1 2 3 4], []]]

35. (defn append [l r]
"Join two lists"
(cond
[(= l []) r]
[True
(cons (car l) (append (cdr l) r))]))
;; (append [1 2] [3 4])
;; => [1 2 3 4]
;; NOTE: `True` is like `else`

36. (defn appendo [l r out]
(conde
[(== [] l) (== r out)]
[(fresh [a d res]
(== (cons a d) l)
(== (cons a res) out)
(appendo d r res))]))

37. What now?

38. Hy
Lisp
Clojure
Python
μKanren
miniKanren
core.logic
Relational
Logic
Datalog
Datomic
GraphQL
Prolog

39. What are tests even
anyway?

40. Dependent Types
Theorem Provers
Logic Programming?
NEXT

41. –Paul Graham, “Beating the Averages”
http://www.paulgraham.com/avg.html
“Lisp's power is multiplied by the fact that your
competitors don't get it.”

42. Thank you
Kyle Oba
koba@pasdechocolat.com
@mudphone

43. miniKanren.org

44. (defn appendo [l r out]
(conde
[(nullo l) (== r out)]
[(fresh [a d res]
(conso a d l)
(conso a res out)
(appendo d r res))]))

45. Other
• Python has no case/switch statement? WTF?
• https://www.python.org/dev/peps/pep-3103/
• http://www.pydanny.com/why-doesnt-python-have-switch-case.html
• but pattern matching is like that on crack, so…
• miniKanren
• https://github.com/algernon/adderall in Hy
• https://github.com/jtauber/pykanren in Python
• what about μKanren?
• https://github.com/jasonhemann/microKanren
• https://github.com/jasonhemann/microKanren/blob/master/microKanren.scm
• http://webyrd.net/scheme-2013/papers/HemannMuKanren2013.pdf