stagePlanner.go
func mirrorStageSubtree(stages []*evaluationStage) {

	var rootStage, inverseStage, carryStage, frontStage *evaluationStage

	stagesLength := len(stages)

	// reverse all right/left
	for _, frontStage = range stages {

		carryStage = frontStage.rightStage
		frontStage.rightStage = frontStage.leftStage
		frontStage.leftStage = carryStage
	}

	// end left swaps with root right
	rootStage = stages[0]
	frontStage = stages[stagesLength-1]

	carryStage = frontStage.leftStage
	frontStage.leftStage = rootStage.rightStage
	rootStage.rightStage = carryStage

	// for all non-root non-end stages, right is swapped with inverse stage right in list
	for i := 0; i < (stagesLength-2)/2+1; i++ {

		frontStage = stages[i+1]
		inverseStage = stages[stagesLength-i-1]

		carryStage = frontStage.rightStage
		frontStage.rightStage = inverseStage.rightStage
		inverseStage.rightStage = carryStage
	}

	// swap all other information with inverse stages
	for i := 0; i < stagesLength/2; i++ {

		frontStage = stages[i]
		inverseStage = stages[stagesLength-i-1]
		frontStage.swapWith(inverseStage)
	}
}
func mirrorStageSubtree(stages []*evaluationStage) {

	var rootStage, inverseStage, carryStage, frontStage *evaluationStage

	stagesLength := len(stages)

	// reverse all right/left
	for _, frontStage = range stages {

		carryStage = frontStage.rightStage
		frontStage.rightStage = frontStage.leftStage
		frontStage.leftStage = carryStage
	}

	// end left swaps with root right
	rootStage = stages[0]
	frontStage = stages[stagesLength-1]

	carryStage = frontStage.leftStage
	frontStage.leftStage = rootStage.rightStage
	rootStage.rightStage = carryStage

	// for all non-root non-end stages, right is swapped with inverse stage right in list
	for i := 0; i < (stagesLength-2)/2+1; i++ {

		frontStage = stages[i+1]
		inverseStage = stages[stagesLength-i-1]

		carryStage = frontStage.rightStage
		frontStage.rightStage = inverseStage.rightStage
		inverseStage.rightStage = carryStage
	}

	// swap all other information with inverse stages
	for i := 0; i < stagesLength/2; i++ {

		frontStage = stages[i]
		inverseStage = stages[stagesLength-i-1]
		frontStage.swapWith(inverseStage)
	}
}
/*
	Performs a "mirror" on a subtree of stages.
	This mirror functionally inverts the order of execution for all members of the [stages] list.
	That list is assumed to be a root-to-leaf (ordered) list of evaluation stages, where each is a right-hand stage of the last.
*/