Type parameter a family?

[Siddhartha Gadgil]

I have a trait with a type parameter and a couple of implementations, say

trait FD[A]

case class FDS[A](...) extends FD[A]

case class FDV[A](...) extends FD[A].

I want a class with a type parameter where I choose a specific implementation, but will use various parameters A. If there were no parameter A, I would write

class Dyn[MyFD <: FD](...)

My question: Is there any way to achieve this with a family of types as above?

Thanks,

Siddhartha

[Daniel Armak]

I’m not sure what you want to accomplish. One option is to write class Dyn[A, MyFD <: FD[A]](...). Then you can use the concrete type of A inside Dyn. If you want to constrain A too, you can write class Dyn[A <: A1, MyFD <: FD[A]](...).

​

Daniel Armak

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[Siddhartha Gadgil]

I actually have several types A, so I cannot use that. The one option I thought of was to use a trait with
type MyFD[A] <: FD[A]

The underlying reason is to make my implementation of FD a value class, and avoid creating it, so methods in the class Dyn should have types the specific implementation and not FD[A]. Presently I have FD[A], and that code is logically correct.

Thanks
Siddhartha