Scala diamond problem and its solution - linearization

1. Scala Diamond
Tomer Ben David

2. Got your fiance a diamond?

3. Let’s hope she is not a software
developer

4. Because if she is...

5. You should think of another trick

6. Fortunately, there is a way out

7. How do you ask?

8. Did you tell her about scala diamond
linearization?

9. What is it you ask?

10. It’s our way of getting you out of
trouble

11. Just think about it

12. The diamond problem is due to
single parent having multiple
children

13. Scala’s solution

14. We call it linearization

15. What if we made sure every single
parent had only one child?

16. No multiple children for single
parents..

17. No diamond problem

18. So we only need to figure out how to
do this linearization

19. Well its simple follow these simple
steps

20. Start from left

21. B extends A
C extends A
D extends B with C

22. We start with D we have a single
type D all is fine

23. Do you see an “extends” or “with”?

24. Yes, then expand every type with its
supertypes and get rid of the main
type you will have now...

25. Getting rid of the main type
(recursion we work on D) (D) we get
B with C

26. linearize B
(Any with AnyRef with A with B)

27. Linearize C
(Any with AnyRef with A with C)

28. All together now:
(Any with AnyRef with A with B) with
(Any with AnyRef with A with C) with
D

29. Remove duplications from LEFT
→ (Any with AnyRef with A with B)
with (Any with AnyRef with A with C)
with D

30. What do we have (from RIGHT!):
Any with AnyRef with A with B with
with C with D ←
So methods first from D then from C
then from B … you get the idea

31. Good Luck Man!