Returning List[Double], Map[String, Double] from a list of Doubles - scala

Question

I'm trying to return a tuple of a list and map. I've already gotten the list to compile correctly however I'm not sure how to use a map and list to get a map of the keys and values that match what's in my list. Here is what I have so far:
I've been able to achieve returning a list. However I need to return (List[Double], Map[String, Double])
def emulateSingleInstruction(stack: List[Double],
env: Map[String, Double],
ins: StackMachineInstruction): (List[Double], Map[String, Double]) = {
ins match{
case AddI => stack match{
case i1 :: i2 :: tail => (i1 + i2 :: tail, env)
case _ => throw new IllegalArgumentException()
}
//USE V1 and V2
case SubI => stack match{
case i1 :: i2 :: tail => (i1 - i2 :: tail, env)
case _ => throw new IllegalArgumentException()
}
case MultI => stack match{
case i1 :: i2 :: tail => (i1 * i2 :: tail, env)
case _ => throw new IllegalArgumentException()
}
//USE V1 and V2
case DivI => stack match{
case i1 :: i2 :: tail => (i1 / i2 :: tail, env)
case _ => throw new IllegalArgumentException()
}
case ExpI => stack match{
case Nil => throw new IllegalArgumentException()
case head :: tail => {
(scala.math.exp(head) :: tail,env)
}
}
case LogI => stack match{
case Nil => throw new IllegalArgumentException()
case head :: tail => {
if (head > 0){(scala.math.log(head) :: tail,env)}
else{ throw new IllegalArgumentException()}
}
}
case SinI => stack match{
case Nil => throw new IllegalArgumentException()
case head :: tail => {
(scala.math.sin(head) :: tail,env)
}
}
case CosI => stack match{
case Nil => throw new IllegalArgumentException()
case head :: tail => {
(scala.math.cos(head) :: tail,env)
}
}
case PushI(f) => (f :: stack,env)
case PopI => stack match{
case Nil => throw new IllegalArgumentException()
case i1 :: tail => {
(tail,env)
}
}
}
}

Answer 1

Since your example operation seems not to modify the environment but only the stack, I understand you are simply asking how to combine the new stack and the environment in the return value.
def emulateSingleInstruction(stack: List[Double],
env: Map[String, Double],
ins: StackMachineInstruction): (List[Double], Map[String, Double]) = {
val newStack = ins match {
case AddI => // your code. Looks good...
}
val newEnv = // expression that evaluates to the updated environment
(newStack, newEnv)
}