calculateFirstRightSide: rightSide
	| break firstSet firstSetB set rightSideRule epsilon|
	rightSideRule := RightSideRule withAll: rightSide.
	firstSet := Set new.
	break := false.
	epsilon := true.
	rightSideRule do: [ :sym |
		(break)
			ifFalse: [
				(terminalsSet includes: sym)
					"terminal"
					ifTrue: [
						firstSet add: sym.
						epsilon := false.
						break := true.
					]
					"nieterminal"
					ifFalse: [
						firstSetB := firstDict at: sym.
						set := firstSetB copy.
						(set includes: Eps)
							ifTrue: [ set remove: Eps ]
							ifFalse: [
								break := true.
								epsilon := false.
							].
							firstSet addAll: set.
						].
				].
			].
			(epsilon)
				ifTrue: [
					firstSet add: Eps.
				].
	^firstSet.