Scala Diamond

Tomer Ben David

Got your fiance a diamond?

Let’s hope she is not a software

developer

Because if she is...

You should think of another trick

Fortunately, there is a way out

How do you ask?

Did you tell her about scala diamond

linearization?

What is it you ask?

It’s our way of getting you out of

trouble

Just think about it

The diamond problem is due to

single parent having multiple

children

Scala’s solution

We call it linearization

What if we made sure every single

parent had only one child?

No multiple children for single

parents..

No diamond problem

So we only need to figure out how to

do this linearization

Well its simple follow these simple

steps

Start from left

B extends A

C extends A

D extends B with C

We start with D we have a single

type D all is fine

Do you see an “extends” or “with”?

Yes, then expand every type with its

supertypes and get rid of the main

type you will have now...

Getting rid of the main type

(recursion we work on D) (D) we get

B with C

linearize B

(Any with AnyRef with A with B)

Linearize C

(Any with AnyRef with A with C)

All together now:

(Any with AnyRef with A with B) with

(Any with AnyRef with A with C) with

D

Remove duplications from LEFT

→ (Any with AnyRef with A with B)

with (Any with AnyRef with A with C)

with D

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

Good Luck Man!