can someone explain this auto type? (when doing

flowOf(1, 1.0, 2, 2.0)

)… don’t understand the

&

&

here reads as

and

. The types here are comparable to any type that is

Double

and

Int

at the same time (such types don’t exist, but compiler does not check that) and extend

Number

.

Why doesn't it just resolve to

Number

?

Because

Comparable<Double & Int>

is more precise than

Number

But

Double & Int

is impossible? A type cannot be both at once.

Comparable<Double | Int>

would make sense to me.

It's a union type, it can be either double or int.

Think about actually using the interface: if I want to call

compareTo

I need to give sometime that is both an

Int

and a

Double

for it to work. Obviously that's impossible, but the type system doesn't know that.

@diesieben07 my example is union. The initial one is intersection

True. I need to think about this more 😄

@karelpeeters as far as I understand the type system does know (otherwise type inference would never work), tots just that the compiler doesn't care. There was an article on intersection types in inference and why they're different from actual types but I can't find it anymore.

Okay, but that doesn't change what I said:

Int & Double

does make sense,

Int | Double

wouldn't.

Ah, now I see it. I've always assumed that Java's

Number

is

Comparable

but it isn't. So the initial type basically reads

this is a Number which is Comparable but you can't actually use generic elements of Comparable because the possible type arguments are disjoint up to but excluding Any Number

(

out

may work as Any Number but Comparable has no type arguments in out position)

Not sure about "up to but including",

Any

doesn't work either.

Nothing

does 😒imple_smile: But yeah, that what it means.

Yeah it depends on the projection. I've just updated my message :)

please give

&

syntax for type parameters instead of

where

syntax, JB!

Do you use it often? Just remember, that are so few ascii characters — each one is precious.