'How recursion in scala case class(logical functions)

when I studying programming and the task in scala I crashed the problem

the error code is class type required but Bool found case class TrueBool extends Bool

I try many way but I can't matched type

    sealed trait Bool
case class True[Bool]() extends Bool
case class False[Bool]() extends Bool
case class And[Bool](elem1: Bool ,elem2: Bool) extends Bool
case class Or[Bool](elem1: Bool, elem2: Bool) extends Bool
case class Neg[Bool](elem1: Bool) extends Bool
case class Imply[Bool](elem1: Bool, elem2: Bool) extends Bool

def formula(fma: Bool): Boolean = fma match {
  // use recursion function and make consist of logical operation Neg, Or, And, Imply 
  case True() => true
  case False() => false
  case And(elem1, elem2) => if(formula(elem1) && formula(elem2)){
    return true
  }else{
    return false
  }
  case Or(elem1, elem2) => if(formula(elem1) || formula(elem2)){
    return true
  }else{
    return false
  }
  case Neg(elem1) => if( formula(elem1) ){
    return false
  }else{
    return true
  }
  case Imply(elem1, elem2) => if(formula(elem1)){
    if(formula(elem2)){
      return true
    }else{
      return false
    }
  }else{
    return false
  }
}

println("** p10 **")
val fma = Imply(And(True, Or(True, False)), False)
println(formula(fma))

}

scala

Solution 1:^[1]

case class True[Bool]() extends Bool

I do not think this does what you want. You introduce a type parameter Bool, which is completely unrelated to your Bool trait.

You cannot extend a (generic) type parameter. This is the same as:

case class True[B]() extends B

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Solution 1	Suma

'How recursion in scala case class(logical functions)

Solution 1:[1]

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Solution 1:^[1]