///|
/// Return a stable execution order: datum steps first, then feature order.
pub fn execution_order(plan : MeasurementPlan) -> Array[MeasurementStep] {
  let ordered = []
  for step in plan.steps {
    if step.direction == "datum-aligned" {
      ordered.push(step)
    }
  }
  for step in plan.steps {
    if step.direction != "datum-aligned" {
      ordered.push(step)
    }
  }
  ordered
}

///|
/// Count how many planned steps use repeated sampling.
pub fn repeated_step_count(plan : MeasurementPlan) -> Int {
  let mut count = 0
  for step in plan.steps {
    match step.strategy {
      RepeatedPoint(_) | Scan(_) => count += 1
      SinglePoint => ()
    }
  }
  count
}