Flattening a sealed case class hierarchy

Question

Suppose I have a sealed case class hierarchy like the following:

sealed trait Expr
case class Const(val: Double) extends Expr
case class Plus(x: Expr, y: Expr) extends Expr
case class Times(x: Expr, y: Expr) extends Expr

• Is it possible to automatically convert expressions such as Plus(1,Plus(2,3)) into a HList of HLists?
• Will the conversion work even inside some function f(e: Expr) , ie when the specific structure of e is not known at compile time?

Answer 1

事实证明，这已经回答了SO 这里 ，并且有一个相应的例子在无形分发无形-2.1.0-快照。